Importancia Filogenteica Morfologia Peces

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In: Community and Evolutionary Ecology of North American Stream Fishes. William J.

Matthews and David C. Heins (eds.), University of Oklahoma Press, Normal OK. 1987. 310 pp.

17. The Importance of Phylogenetic Constraints in Comparisons of MorphologicalStructure Among Fish Assemblages

Richard E. Strauss

Abstract

Morphological approaches to the study of community relationships are based on the premise that morphological

differences among organisms reflect in large part their ecological relationships and that morphological "space" can be

mapped onto ecological "space." Although morphological characteristics have been used to account for aspects of

foraging and habitat use, phylogenetic effects of form diversity on the repeatability of morphological patterns of variation

among communities are unknown. The morphological structures of several North and South American freshwater fish

assemblages were compared to assess the dependence of morphological congruence on taxonomic similarity. Correlations

of morphological patterns are high (> 0.7) for geographically proximate assemblages, but for comparisons between North

and South American assemblages the average correlation is 0.20. The density at which species are "packed" into

morphospace, and thus the average similarity between species, is independent of the number of species present; within

assemblages, therefore, total size-independent morphological variation is highly dependent on species diversity.

Hypotheses about patterns in natural communities, their

structure and composition, are at the center of current ecolo

gical debate (Cody and Diamond, 1975; Wiens and Roten

berry, 1980a; Anderson et aI., 1981; Strong, 1983; Salt,

1984; Strong et aI., 1984). Important questions are the extc.nt

to which competitive interactions pattern the observed ecolo

gical and morphological relationships of species within com

munities, and to what degree the ecological functions

(niches) of members can be predicted from their morpholo

gical characteristics. The assumption of strong correspon

dence between niche and morphology (that is, that morpho

logical "space" maps directly onto ecological "space";

Hutchinson, 1968; Ricklefs and Travis, 1980) is critical to

many community studies. For example, several researchers

have compared patterns of morphological structure among

communities (Ricklefs and O'Rourke, 1975; Findley, 1973,

1976; Gatz, 1979b; Ricklefs and Travis, 1980; Ricklefs et

al., 1981) or expressed relative niche characteristics in terms

of morphological differences among species (Hespenheide,

1973; Gatz, 1979a) . Yet congruence between morphology

and ecology is seldom tested directly (Felley, 1984; Miles

and Ricklefs, 1984).

It is evident that morphological characteristics can be used

to predict aspects of foraging behavior and habitat use (Fla

nagan, 1981; Gatz, 1979b, 1981; Findley and Black, 1983;

Miles and Ricklefs, 1984). However, a considerable amount

136

of residual morphological variation in many communities

cannot be related directly to ecological variables (Weins and

Rotenberry, 1980b; Felley, 1984), reducing the predictabil

ity of morphological relationships in one assemblage from

those observed in another. An additional confounding factor

is faunal composition: if the historical pool of taxonomic

"morphotypes" has been very different for two assem

blages-that is, if the communities being compared are com

prised of species derived from sets of independent evolution

ary lineages-then the resulting morphological patterns

could differ profoundly. How might morphological structure

be affected, for example, when characins are "substituted"

(in a historical sense) for cyprinids? Two possibilities are (1)

that ecological (e.g ., hydrodynamic, foraging) factors are so

important in sorting out sets of coexisting species that the

major patterns of variation remain relatively stable among

communities, irrespective of the actual species present, or

(2) that differences in body form among major evolutionary

lineages are large enough to override small-scale, localized

ecological pressures, so that, for example, North American

stream-fish communities might be structured very differently

from corresponding South American communities. In the

latter case some degree of correspondence in major patterns

of morphological variation might be evident once phylogene

tic constraints (taxonomic similarities) have been taken into

account.



The Importance of Phylogenetic Constraints in Comparisons of Morphological Structure 137

Table 17.1. Localities and Their Taxonomic Composition*

Number of Collection

LocalityFamilies Genera Species Individuals

No. Areat

Sites

1. Little Fishing Creek, PA 8 19

Pennsylvania2. Yellow Breeches Creek, PA 6 15

Pennsylvania

3. Lake Opinicon, ON 8 14

Ontario

4. Big Sandy Creek, TX 8 16

Texas

5. Martis Creek, CA 5 9

California

6. Rio Parana, PY 9 31

Paraguay

7. Rio Aquidaban, PY 5 21

Paraguay

8. Composite 22 22

'Taxa are given in the Appendix.

'Sampled length of stream or surface area of lake.

To explore such questions in detail, I initiated a study of

morphological variation among freshwater fish assemblages

collected from a variety of climatic regions and having vary

ing degrees of taxonomic similarity to one another. Specifi

cally, the study was designed to answer the following ques

tions: (l) What are the major patterns of variation, in

dependent of ontogenetic effects on body form, among fishes

in stream assemblages? (2) Are patterns of variation con

sistent among assemblages from different habitats? (3) Is

degree of concordance dependent on faunal composition? Ifso, at what taxonomic level? (4) Is the overall level of

similarity, the degree to which species are "packed" into

morphological space, dependent on the number or composi

tion of species present? And does packing density differ for

temperate versus subtropical habitats?

Materials and Methods

Localities and Taxonomic Composition

Localities were chosen to represent differing habitats and

taxonomic assemblages (table 17.1). Assemblages were rep

resented by series of fish collections taken within a limited

region (less than 25 km linear extent) of the watershed.

Localities and associated collections were selected from

three different sources: personal records, selected literature

records, and museum expedition records.

The two Pennsylvania localities (PA) were extensively

sampled in 1978-79; all specimens were deposited in the

Pennsylvania State University research collections. Lake

Opinicon, Ontario (ON; Keast and Webb, 1966; Keast,

1978b), Big Sandy Creek, Texas (TX; Evans and Noble,

1979, stations 3-5), and Martis Creek, California (CA;

Moyle and Vondracek, 1985) had been surveyed by the

authors cited. On the basis of their species lists and de

scriptions, I located collections in the University of Michigan

28 176 6 12 km

23 138 4 14 km

16 114 5 8 km2

30 186 3 12 km

12 78 4 3 km

38 240 5 16 km

24 158 5 24 km

22 290

Museum of Zoology (UMMZ) that corresponded as nearly as

possible to the cited geographical locations and that had been

collected in similar habitat, especially lake versus stream

(similar studies that lacked corresponding UMMZ col

lections were disregarded). These collections were consid

ered to be representative of the described assemblages, under

the reasonable assumption that intraspecific geographic var

iation is negligible in relation to ontogenetic and interspecific

variation. The two Paraguayan (PY) localities were selected

from a large survey conducted by the UMMZ Paraguayan

Expedition of 1979. All specimens examined were taken

directly from those collections.

Because the North American and the Paraguayan assem

blages had virtually no faunal overlap, a composite sample

was assembled by pooling data on one species from each of

22 families represented in the study (see Appendix). Species

were chosen to maximize taxonomic overlap among locali

ties. In several analyses of morphological structure this com

posite was treated as an independent assemblage, though the

data comprising it were replicated from the other samples.

Measures of taxonomic similarity (S) among assemblages

were based on Dice's (= Sorenson's) index, S = 2N)(N, +

N2) ' where N, and N2 are the numbers of taxa in two assem

blages and Nc is the number held in common. The index

ranges from 0 to I and is linearly proportional to the propor

tion of shared taxa (Cheetham and Hazel, 1969). Indices

were computed separately for species, genera, and families;

the three values were averaged to give a composite measure

of taxonomic similarity. This procedure diminishes the effect

of taking at face value the names and ranks assigned to taxa,

particularly for South American groups taxonomic treat

ments of which have been uneven in scope and quality.

Cluster analyses of assemblages in relation to taxonomic

structure were performed on the l ' s complements of similar

ity values (D = 1 - S = [N, + N2 - 2NcJ/[N, + N2]) using

the UPGMA clustering algorithm (Sneath and Sokal, 1973).



138 Community and Evolutionary Ecology of North American Stream Fishes

Description of Morphology

The biological reliability of any morphological study is criti

cally dependent on how form and form differences are quan

tified and analyzed (Strauss and Bookstein, 1982; Bookstein

et a!., 1985). The geometric and statistical methods used in

this study were chosen (1) to provide a fairly complete

morphological description of each species, unbiased by priorfunctional expectations; (2) to encompass sets of functionally

analogous anatomical reference points (= landmarks); (3) to

explicitly include information on ontogenetic (allometric)

variation; and (4) to allow forms to be archived and recon

structed.

Species in each assemblage were represented by 5-12

specimens, deliberately chosen to give the largest size range

possible (from 1: 1. 5 to 1: 17, smallest:largest standard

lengths). All species were used except for several extreme

phenotypes: anguillids, synbranchids, gymnotids, and rham

phichthyids. Data consisted entirely of mensural characters

(distances measured with respect to anatomical landmarks).

Specimens were photographed in lateral aspect, withaccompanying metric scale, with the use of small insect

mounting pins to locate midsagittal landmarks (e.g., anus,

supraoccipital crest) that could not easily be seen from lateral

view. Landmarks (fig. 17.1) were marked on each photo

graph and digitized as Cartesian coordinates. Euclidean dis

tances were subsequently computed between pairs of scaled

landmark coordinates; distances were selected to form' 'trus

ses" (fig. 17.1 A; Strauss and Bookstein, 1982) and addition

al combinations of measurements in lateral projection (fig.

17.1 B). Auxiliary measurements of body width, taken with

digital calipers into a computer file, were used to approxi

mate a triangulation in dorsal projection (fig. 17 .IC); bilater

al measurements were averaged before analysis. Body-widthmeasurements and distances across the abdomen were

selected to be minimally affected by variation in volume of

gas bladder, gut, or ovaries. The resulting data set adequately

describes the major features of external body form, including

body proportions and relative sizes and positions of mouth,

eye, head, and fins. It omits information about complex fin

shapes; degree of separation of dorsal fins; adipose fins,

barbels, and other specialized appendages; and internal anat

omy.

Morphological Space

Analyses are based on the positions of specimens in a multi

dimensional morphological hyperspace (morpho space) the

axes of which are logarithms of the 54 mensural characters.

The logarithmic transformation linearizes allometries, stan

dardizes variance, and produces a scale-invariant covariance

matrix (Bookstein et a!., 1985).

Ontogenetic size variation was explicitly included as a

major factor by an examinination of secondary size

independent patterns of variation with respect to multivariate

size factors. This procedure takes into consideration the

substantial changes in form that occur during growth. It also

negates the necessity of arbitrarily limiting size ranges to

"adults. "

The full morphospace was reduced by means of principal

component analysis (PCA) of the covariance matrix (Book

stein et a!., 1985). Use of the covariance matrix preserves

allometries and leaves the geometric space undistorted, so

that Euclidean distances based on original log measurements

and on principal component scores are identical. Because of

the large size ranges within and among species, the first

component was in all cases a strong size vector, accounting

for> 72% of the total variance within assemblages and>

97% of the variance within species, with consistently posi

tive loadings. The first five components always accountedfor> 98% of the variance among species; thus the sixth and

subsequent components were disregarded for multivariate

comparisons (but not for calculation of nearest-neighbor

distances). For size-free comparisons among assemblages,

sheared principal components (Humphries et a!., 1981;

Bookstein et al., 1985) were computed by regressing out the

pooled within-group size factor (PC 1) while maintaining t?e

group centroids. Sheared components are ver;: stable d.lS-

criminant axes that are unaffected by differences II I mean size

among groups.

A

c ~ ~i _ - ----- ---------

Fig. 17.1. The set of 56 mens ural characters used for morphoI?etric

analyses. Anatomical landmarks are indicated by open Circles;

distance measures, by dotted lines. A: Midsagittal truss measures.

B: Auxiliary measures in lateral projection. C: Auxiliary measures

in dorsal projection.



The Importance of Phylogenetic Constraints in Comparisons ofMorphological Structure 139

Assessment of pairwise congruence of morphological var

iation among assemblages was based on shared principal

component analyses. For each pairwise comparison the data

for two assemblages were pooled, PCs were extracted, and

PC I was sheared (regressed) from components 2-5. Within

this reduced size-free space, loadings can be represented asvector correlations (directional cosines; Wright, 1954), es

timated for each mensural character by its correlations withprojection scores across individuals (fig. 17.3). The correla

tion between assemblages for each character is the cosine of

the angle between corresponding vectors. Mean character

correlation was estimated by standardizing all character cor

relations between assemblages with arc sine transformations

(Sokal and Rohlf, 1981) and reconverting the mean value

across characters with an inverse arc sine transformation.

Species-packing analyses were based on PCAs performed

separately for each assemblage. Size-independent nearest

neighbor distances (NNDs) were computed within the re

duced (n - I, for n characters) PC space from which the first

component had been sheared. Distributions of NNDs were

compared against random models using the method of Donnelly (1978) and Sinclair (1985).

Results

Similarity in Faunal Composition Among Assemblages

The two PA and two PY assemblages were initially intended

to be pairs of "replicates" sampled from within major drain

age basins. The PA samples are similar at all three taxonomic

levels (table 17.2), except for the presenceof ictalurids and a

cyprinodont at Little Fishing Creek and for several sub

stitutions of congeneric species. The Paraguayan assem

blages are much less similar to one another than is the PA pair

owing to the presence of a diverse collection of catfishes at

the RIO Parana locality. The ON, TX, and CA groups share

intermediate numbers of taxa at all taxonomic levels. The CA

assemblage, which is small and has a high degree of endem

ism (Moyle and Vondracek, 1985), is the most dissimilar

among the North American assemblages. As expected, there

is almost no faunal overlap between the Paraguayan and the

North American groups; Rio Parana and Little Sandy Creek

AJI

I

L

BI

L

I

1.0 .8 .6 .4 .2

Mean Taxonomic Difference

I

0

PA

PA

ON

TX

CA

PY

PY

PA

PA

ON

TX

CA

Composite

PY

PY

Fig. 17.2. Dendrograms of assemblages clustered by taxonomic

dissimilarity, excluding (A) and including (B) the composite sampie. Locality abbreviations are given in table 17.1.

Table 17.2. Numbers of Species, Genera, and Families Shared Among Assemblages (Above Diagonal), and Associated Measures ofTaxonomic Similarity (Below Diagonal)

Locality1 2 3 4 5 6 7 8

PA PA ON TX CA PY PY Composite

1. PA 17, 12,5 7, 8, 6 3, 10,7 0,4,4 0, 0, 0 0,0,0 6,7,8

2. PA 0.70 5, 6, 3 2, 6, 4 1, 5, 5 0, 0, 0 0,0,0 5,6,6

3. ON 0.52 0.39 3, 8, 6 0, 1, 2 0, 0, 0 0,0,0 6,8,8

4. TX 0.52 0.35 0.47 1, 1, 3 0,0, 1 0,0,0 1,7,8

5. CA 0.30 0.46 0.13 0.20 0,0,0 0,0,0 1,4,5

6. PY 0.00 0.00 0.00 0.04 0.00 9, 13,4 8,8,9

7. PY 0.00 0.00 0.00 0.00 0.00 0.45 5, 5, 5

8. Composite 0.37 0.32 0.43 0.31 0.23 0.38 0.27




Fig.17.3. A: Scatterplot of projections of all Aspecimens within the plane of the second and ~ ~ - - - - - - - - = - : ' ~ . . . ,third sheared (size-independent) principal 1"X

B

components, based on 54 mensural charac

ters. Convex polygons enclose all points

within corresponding assemblages; pairs of 1'0U

assemblages from P A and PY have been com- a...

bined. B: Selected character vectors portray- "0

ing correlations of characters with the corre- osponding principal components of panel A. C1)

.s::.

(J')

bodydepth

headlength

predorsal length~ : : : : : : : - -

Igape

preanal Ilength

body length

Sheared PC2 Correlation with PC2

possess a single but different poeciliid each. Dendograms of

the assemblages (fig. 17.2) provide an overall assessment of

taxonomic similarity.

Congruence of Morphological Distribution

All assemblages overlap considerably in morphological

space, and no pairwise combinations of localities could be

discriminated (fig. 17.3). However, species are not distrib

uted evenly or randomly within assemblages; observed dis

tributions of nearest-neighbor distances indicate that species

are significantly clustered, with NNDs both longer and short

er than expected based on random models.

Comparisons of assemblages in the sheared PC space of

fig. 17.3 are meaningful only to the extent that the within

assemblage size vectors (within-group PC 1 axes) are parallel

within the full morphological space (Humphries et a1.,

1981). Pairwise correlations among size vectors are all >0.90 (table 17.3), indicating that PC 1 as a multivariate

measure of body size is highly consistent across species and

assemblages.

Mean character vectors within the sheared PC space (fig.

17. 3B) characterize the major size-independent trends in

body form within and among assemblages. At a given body

size species vary from elongated forms (lower right of fig.

17. 3B) with relatively wide body, posteriorly displaced me

dial fins, and wide oral gape, to deep-bodied, narrow forms

(upper left). Size of the head and associated cephalic features

(snout length, eye diameter, posterior displacement of pec

toral fin, etc.) are more or less independent of this morpho-

cline. These and other associated trends are generally con

sistent with the major shape variations observed by Flanagan

(1981) for marine reef fishes. Note that these are average

character correlations across all assemblages; as described

below, the trends within any particular assemblage deviatefrom these to some extent.

Patterns of Species Packing

The average morphological "density" of species within

assemblages, as indicated by mean nearest -neighbor distance

(NND), is not a function of number of species (fig. 17.4A).

Species in diverse assemblages are neither more nor less

similar than species in depauperate ones. The slight nonsig

nificant trend of decreasing distance with increasing number

in fig. 17.4A is due to the influence of the two Paraguayan

assemblages, which have slightly smaller (but not signifi

cantly different) mean NNDs from thoseof

the North American assemblages. However, when total occupied morpho

logical space (that is, total size-independent variance sub

sumed) is examined as a function of diversity (fig. 17.4B)

there is a significant positive relationship, indicating that the

total space occupied (total variance) increases in proportion

to the number of species present. Again, the Paraguayan

species are relatively more similar to one another than are the

North American species. For example, the Rio Parana

assemblage, with 38 species, has approximately the same

total variance as a PA assemblage having 28 species; and the

Rio Aquidaban, with 24 species. has about the same variance

as Lake Opinicon, with only 16 species.

Table 17.3. Pairwise Correlations Among Size Vectors (Within-Assemblage PC 1) (Above Diagonal) and Among Sets of Character Vectors

(Below Diagonal)

I 2 3 4 5 6 7Locality

PA PA ON TX CA PY PY

1. PA 0.99 0.97 0.96 0.96 0.93 0.93

2. PA 0.77 0.97 0.96 0.96 0.95 0.95

3. ON 0.44 0.42 0.98 0.96 0.94 0.94

4. TX 0.63 0.49 0.73 0.96 0.93 0.94

5. CA 0.37 0.71 0.28 0.24 0.91 0.91

6. PY 0.32 0.25 0.19 0.20 0.07 0.98

7. PY 0.28 0.17 0.16 0.34 0.26 0.44



The Importance of Phylogenetic Constraints in Comparisons of Morphological Structure 141

Q)

.5c0

--/')(5 4....0

.. 0

..c(J'l .3'(i)

ZI

-- .2/')

Q)....0Q)

Z .1c0Q)

Z

.8Q)

uco.....7

~g .6

(J'l

oo

..c .50. .....

o

Z .4

ATX

PA •CA

--·-ON •

.--- p 'A - - - py-py 0

0

r = 0.29

p= 0.26

10 20 30 40

Number of Species

B TX•

PA /.

• PA py~ . 0

ON P1CA/ • r= 0.66

/.

p=0.05

10 20 30 40

Num ber of Species

Fig. 17.4. Scatterplots of (A) mean nearest-neighbor distances and(B) total size-independent morphological variance as functions ofnumber of species within each assemblage. Variance is expressed as

a percentage of total size-independent variance among all assemblages. Solid circles = North American localities; open circles =South American localities. The expected grand-mean NND forrandomly distributed points would be 0.51; observed values are

significantly less than expected, indicating aggregation.

Distributions of NNDs are significantly nonrandom (P

«0 . 0 1 ) for all assemblages and indicate clustering within

morphospace with respect to random models. This

nonrandomness could be due to phylogenetic patterning, in

that confamilial and congeneric species might be expected to

aggregate and to be distant from less closely related species

(Gatz, 1979a). To examine this possibility, NND distribu

tions were determined for cyprinids in the two PA assem

blages and for characids in the two PY assemblages; of the

families studied, these were the only ones having sufficient

numbers of species for comparison. In all four cases NND

distributions were not significantly different from random

(though somewhat overdispersed), indicating that the mor

phospace aggregations do correspond to taxonomic group

ings at the family level.

Congruence of Morphological Structure

Mean character correlations, estimated among all possible

pairs of assemblages (table 17.3), range from 0.77 between

the two PA localities to a nonsignificant 0.07 between the CA

and Rio Parana (PY) assemblages. The high congruence

between the PA "replicates" is not surprising; if two such

localities had exactly the same species composition, their

patterns of morphological variation should be identical ex

cept for minor differences owing to geographic variation.

However, there is no prior expectation for correlations be

tween North American and South American assemblages,

which actually range from 0.07 (CA-PY) to 0.34 (TX-PY)

with a mean correlation of 0.20. Such low correlations seem

to indicate that phylogenetic differences among componentspecies are more important than ecological constraints in

determining overall patterns of morphological structure .

Moreover, the effect of taxonomic similarity is clinal

rather than discrete. The linear relationship between mean

character correlation and taxonomic similarity (fig. 17.5) is

highlysignificant(r = 0.82,t = 7.3,df= 26,P«0.0 l) .

Thus assemblages having intermediate levels of taxonomic

similarity are also intermediate in morphological con

gruence. The regression function, when extrapolated to the

case of identical faunal composition (S = I), gives a pre-

c0

•-

0• •)

....~• •U

••

• •• •

Q).5-

()

0~•

• r=0.82

••

0...c: ••c I0Q) I·~

•0

0 .5

Mean Taxonomic Similarity

Fig. 17.5. Scatterplot of morphological congruence as a function oftaxonomic similarity for all pairs of assemblages, including thecomposite. Each point represents one assemblage pair. The regres-sion line assumes independent residuals; observed residual correlations were statistically negligible.




dicted mean character correlation not significantly different

from the expected 1. The predicted mean correlation of 0.20

for complete taxonomic dissimilarity is a measure of the

amount of congruence expected from ecological constraints

acting alone.

Discussion

Morphological approaches to descriptive analyses of com

~ u n i t y relationships are based on the premise that morpholo

gical features of organisms reflect in large part their ecologi

cal relationships, or at least that morphological analyses may

reveal patterns of structure that require explanation in the

context of ecological and evolutionary theory (Ricklefs and

Travis, 1980; Douglas, chap. 18). The concept of morpho

logical structure within a community or assemblage has had a

dual context in the literature, being used in some cases to

indicate the spatial patterns of species within the morpho

space, particularly in terms of distances between species and

overlap among groups of species, and in other cases toindicate patterns of variation among morphological charac

ters. Because convergence in body form and other features

seems to be widespread among fishes in both freshwater and

marine habitats (at least at a gross morphological level), it

might seem likely that the ecological interactions that sort out

coexisting combinations of species may structure assem

blages in predictable ways, even if a one-for-one replace

ment of species in different habitats does not occur (Schlosser, 1982a).

The results of this study, however, suggest that the ability

to predict patterns of variation among communities is limited

by the degree to which the component species have been

derived from a common evolutionary and biogeographicbackground. Thus a serious methodological problem con

cerns the scale of sampling. Population sizes and degrees of

ecological overlap among species may vary widely both

spatially and temporally, and the detection of repeatable

patterns may be a critical function of the scale on which

ecological processes act, particularly in relation to magni

tudes of gene flow among populations inhabiting different

communities and experiencing varying combinations of

predators, prey, competitors, and physical-habitat character

istics. Nevertheless, these results should serve as a caveat for

the comparative study of ecomorphological patterns. When

the communities chosen for study lie within the same

biogeographic or faunal region, a high degree of concordance is to be expected (e.g., Gatz, 1979a, 1981).

Schoener (1974) originally suggested that the total amount

of " ~ i c h e space" occupied by an assemblage of coexisting

species should enlarge as the number of extant species in

creases, because additional species may utilize previously

unused aspects of the available ecological resources. This

hypothesis has been tested indirectly by a number of in

vestigators using morphological analysis (e.g., Karr and

James, 1975; Findley, 1973, 1976; Ricklefs and O'Rourke,

1975; Gatz, 1979a; Ricklefs and Travis, 1980; Ricklefs et

al., 1981; Findley and Black, 1983). Their results, and those

of this study, have generally supported Schoener's hypothe

sis that the "core" of the community space, consisting of

relatively unspecialized species, is ecologically saturated

and that species are added to a community in secondary or

novel directions. An alternative explanation is that the eco

logical conditions of less diverse communities are favorable

only to generalist species (Ricklefs and Travis, 1980);however, the continuous relationship between total morpho

logical variance and species number, demonstrated in this

study, would argue against a hypothesis invoking response to

harsh or variable environments as a general controlling

mechanism. A possible mechanism for the assemblage of

freshwater fishes into specific habitats is the sorting out from

the regional source pool of species (both specialized and

un specialized) that can coexist in the short term, with minor

subsequent modification following from competitive ecolog

ical interaction.

These findings are complementary to those of Mayden

(chap. 26) in demonstrating that an understanding of the

history of a communityis

an important prerequisite to assessing the degree to which morphological features have been

molded by competition or other ecological interactions (see

also Brooks, 1985). In the absence of detailed knowledge

about the phylogenetic relationships of component taxa and

the geological history of the regions under study, it is impos

sible to judge the extent to which extant communities have

resulted from recent coevolutionary processes versus the

chance assemblage of historically available species. In such

cases assessment of faunal similarity will at least provide a

rough estimate of the amount of morphological congruence

expected among assemblages in the absence of adaptive

modifications.

In summary, the hydrodynamic and competitive con

straints imposed by the aquatic environment do not necessar

ily lead to morphological similarity among assemblages by

way of evolutionary convergence, at least with regard to

patterns of variation among species. The teleost "morpho

type" seems to be sufficiently flexible that morphological

structure need not be highly constrained in similar ways in

different habitats. Instead, each characteristic body fOlm

exploits the aquatic environment somewhat differently in

terms of its own morphological and ecological design, and

resultant differences among species (in magnitude and direc

tion) are highly variable. Thus phylogenetic patterns of form

diversity are responsible both for consistency among differ

ent fish assemblages within the same biogeographic regions

and for noncongruence among assemblages having little

faunal similarity. I

IThe University of Michigan Morphometries Study Group served as the

forum in which much of my philosophy about biological form and geometric

morphometry was developed, and I am grateful to the participants: F. L.

Bookstein, B. Chernoff, R. L. Elder, J. M. Humphries, and G. R. Smith. Ithank E. L. Cooperfor use of the PSU collections, and R. R. Miller, G. R.

Smith, and W. L. Fink for use of the UMMZcollections. Critical comments

by M. E. Douglas, M. A. Houck, and G. D. Schnell substantially improved

the manuscript. National Science Foundation grant BSR -8307719 provided

financial support.



LITERATURE CITED

Anderson, G. R. V., A. H. Ehrlich, P. R. Ehrlich, J. D. Roughgarden, B. C. Russell, and F. H.

Talbot. 1981. The community structure of coral reef fishes. Am. Nat. 117:476-495.

Bookstein, F. L., B. Chemoff, R. L. Elder, J. M. Humphries, G. R. Smith, and R. E. Strauss. 1985.

Morphometrics in Evolutionary Biology. Spec. Publ. No. 15, Acad. Natl. Sci. Phila., PA.

Brooks, D. R. 1985. Historical ecology: a new approach to studying the evolution of ecological

associations. Ann. Missouri Bot. Garden 72:660-680.

Cheetham, A. H., and J. E. Hazel. 1969. Binary (presence-absence) similarity coefficients.

J. PaleontoI. 43:1130-1136.

Cody, M. L., and J. M. Diamond (ede.). 1975. Ecology and Evolution of Communities. Belknap

Press, Cambridge, MA.

Donnelly, K. 1978. Simulations to determine the variance and edge-effect of total nearest neighbor

distance. In: I. Hodder (ed.), Simulation Methods in Archaeology, pp. 91-95. Cambridge Univ.

Press, London.

Douglas, M. E. 1987. An ecomorphological analysis of niche packing and niche dispersion in stream

fish clades. In: W. J. Matthews and D. C. Heins (ede.), Community and Evolutionary Ecology ofNorth American Stream Fishes, pp. 144-149. University of Oklahoma Press, Norman.

Evans, J. W., and R. L. Noble. 1979. The longitudinal distribution of fishes in an east Texas stream.

Am. MidI. Natur. 101:333-343.

Felley, J. D. 1984. Multivariate identification of morphological-environmental relationships within

the Cyprinidae (Pisces). Copeia 1984:442-455.

Findley, J. S. 1973. Phenetic packing as a measure of faunal diversity. Am. Nat. 107:580-584.

Findley, J. S. 1976. The structure of bat communities. Am. Nat. 110:129-139.

Findley, J. S., and H. Black. 1983. Morphological and dietary structuring of a Zambian

insectivorous ba t community. Ecology 64:625-630.

Flanagan, C. A. 1981. Fourier Morphometrics of Reef Fishes of the Gulf of California. Ph.D.Thesis, Univ. Arizona.

Gatz, A. J. 1979a. Community organization in fishes as indicated by morphological features.

Ecology 60:711-718.

Gatz, A. J. 1979b. Ecological morphology of freshwater stream fishes. Tulane Stud. Zool. Bot.

21:91-124.

Gatz, A. J. 1981. Morphologically inferred niche differentiation in stream fishes. Am. MidI. Nat.

106:10-21.

Hespenheide, H. A. 1973. Ecological inferences from morphological data . Ann. Rev. Ecol. Syst.

4:213-229.

Humphries, J. M., F. L. Bookstein, B. Chernoff, G. R. Smith, and S. G. Poss. 1982. Multivariatediscrimination by shape in relation to size. Syst. Zool. 30:291-308.

Hutchinson, G. E. 1968. When are species necessary? In: R. C. Lewontin (ed.), Population Biology

and Evolution, pp. 177-186. Syracuse Univ. Press, NY.

Karr, J. R., and F. C. James. 1975. Ecomorphological configurations and convergent evolution in

species and communities. In: M. L. Cody and J. M. Diamond (eds.), Ecology and Evolution of

Communities, pp. 258-291. Belknap Press, Cambridge, MA.

Keast, A., and D. Webb. 1966. Mouth and body form relative to feeding ecology in the fish fauna of

a small lake, Lake Opinicon, Ontario. J. Fish. Res. Bd. Canada 23:1845-1874.

Keast, A. 1978. Trophic and spatial interrelationships in the fish species of an Ontario temperate

lake. Environ. BioI. Fish. 3:7-31.



,

Strauss 2

Mayden, R. L. 1987. Historical ecology and North American Highland fishes: a research program incommunity ecology. In: W. J. Matthews and D. C. Heins (eds.), Community and Evolutionary

Ecology of North American Stream Fishes, pp. 210-222. University of Oklahoma Press, Norman.

Miles, D. B., and R. E. Ricklefs. 1984. The correlation between ecology and morphology in

deciduous forest passerine birds. Ecology 6 5 : 1 6 2 ~ 1 6 4 0 .Moyle, P. B., and B. Vondracek. 1985. Persistence and structure of the fish assemblage in a small

California stream. Ecology 66: 1-13.

Ricklefs, R. E., D. Cochran, and E. R. Pianka. 1981. A morphological analysis of the structure of

communities of lizards in desert habitats. Ecology 62:1474-1483.

Ricklefs, R. E., and K. O'Rourke. 1975. Aspect diversity in moths: a temperate-tropicalcomparison. Evolution 29:313-324.

Ricklefs, R. E., and J. Travis. 1980. A morphological approach to the study of avian community

organization. Auk 97:321-338.

Sale, P. 1977. Maintenance of high diversity in coral reef fish communities. Am. Nat. 111:337-359.

Salt, G. W. (ed.). 1984. Ecology and Evolutionary Biology: a Round Table on Research. Univ. of

Chicago Press, IL.

Schoener, T. W. 1974. Resource partitioning in ecological communities. Science 185:27-39.Schlosser, I. J. 1982. Fish community structure and function along two habitat gradients in a

headwater stream. Ecol. Monogr. 52:395-414.

Sinclair, D. F. 1985. On tests of spatial randomness using mean nearest neighbor distance. Ecology

66:1084-1085.

Sneath, P. H. A., and R. R. Sokal. 1973. Numerical Taxonomy. W. H. Freeman, San Francisco, CA.

Sokal, R. R., and F. J. Rohlf. 1981. Biometry, !nd ed. Freeman, San Francisco, CA.

Strauss, R. E., and F. L. Bookstein. 1982. The truss: body form reconstructions in morphometries.

Syst. Zool. 31:113-135.

Strong, D. R. 1983. Natural variability and the manifold mechanisms of ecological communities.

Am. Nat. 122:636-660.

Strong, D. R., D. Simberloff, L. G. Abele, and A. B. Thistle (eds.). 1984. Ecological Communities:

Conceptual Issues and the Evidence. Princeton Univ. Press, Princeton, NJ.

Wiens, J. A. 1980. Patterns of morphology and ecology in grassland and shrubsteppe bird

populations. Ecol. Monogr. 50:287-308.

Wiens, J. A., and J. R. Rotenberry. 1980. Bird community structure in cold shrub deserts:

competition Of chaos? Acta XVII Congr. Internat. Ornithol. (Berlin): 1063-1070.

Wright, S. 1954. The interpretation of multivariate systems. In: O. Kempthorne, T. A. Bancroft,J. W. Gowen, and J. L. Lush (eds.), Statistics and Mathematics in Biology, pp. 11-33. IowaState Univ. Press, Ames; IA.

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