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Transcript of Gwen M. Daley [email protected]. I was sitting in the ________________ __________________ when...
Biodiversity Unhinged: Assessing measures of biodiversity in a Pleistocene shell bed
Gwen M. [email protected]
I was sitting in the ________________ __________________ when Richard
Bambach came by. He had been ____________________ and had an idea
about my ___________. After discussing this _____________ idea for _____
_________ , I decided that the idea was ________! I decided to ___________
the idea.
RKB Mad Libs
research space research verb
verb
research activity/topic/product adjective number
unit of timedescriptive
phraseverb
lab sorting shells
watching
counting annoying 20
minutes nuts disregard
Yorktown Samples
WAIT!Why not count all the fragments?
19952014
Why not count al l of the fragments?
COUNTING BIVALVES
A bivalve shell has two valves. Each valve has only one umbo, so a fragment of the valve that contains the umbo indicates the presence of one valve of that species.
The umbo is attached to the hinge structures of the shell, which is usually the most durable part of the valve.
The hinge contains essential morphologic information for identifying bivalve taxa.
Caloosa Shell Quarry Fort Thompson Formation
SAMPLING B-FRAGMENTS
A sample of the Fort Thompson Formation (Pleistocene) from the Caloosa Shell Quarry in Florida was chosen to process.
The sample had previously been processed for paleoecologic material and bivalve hinge fragments (and other material) were removed.
The remaining “picked” material was re-picked. All fragments were classified to the lowest taxonomic level possible. To avoid confusion, non-hinge fragments will be called b-fragments.
sieves
2 kg
Sample Processing
> 4 mm
fragments
> 4 mm1-4 mm>1 mm
~900 g ~330 g ~770 g = 2,000 g
HingeFragment
s
OtherFragment
s
Specimens
Taxa
3,200 6,400 9,600 12,80000
10
20
30
40
RAREFIED DIVERSITY
Caloosa Shell Quarry Fort Thompson Bivalve Hinge Fragment Data
45
Hammer, Ø., Harper, D.A.T., Ryan, P.D. 2001. PAST: Paleontological statistics software package for education and data analysis. Palaeontologia Electronica 4(1): 9pp. http://palaeo-electronica.org/2001_1/past/issue1_01.htm
BIVALVE DIVERSITY
A total of 45 species of bivalves were recovered from the >4 mm sediment size fraction of the 12 Caloosa Shell Quarry samples of the Fort Thompson Formation using hinge fragment data.
500 1000 1500 2000 2500 3000 3500 400000
4
8
12
16
20
24
28
32
36
This sample
RAREFIED DIVERSITY
All FTT samples
3230
Caloosa Shell Quarry Fort Thompson Bivalves
Specimens
Taxa
The species richness as determined by hinge fragments for the specific sample that was re-picked for fragments was 30 species.
The rarefied diversity for the 12 combined Fort Thompson (FTT) samples at 1,100 specimens was somewhat higher.
BIVALVE DIVERSITY
Caloosa Shell Quarry Fort Thompson Formation
SAMPLING B-FRAGMENTS
Chione elevata
gastropodsshell cheese
Anadara transversa
Other bivalves
unsorted
Although other taxa were separated (e.g., barnacles, corals and gastropods), low level classification was only practical for bivalve fragments.
Too Many B-Fragments
Chione elevata (2,070)
Anadara transversa (520)
Anomia simplex (198) Other bivalves
Ostrea equestris (95)
Trachycardium egmontonium
Parvilucina nasula
Mercenaria campechiensis
Dosinia acetabulum
Chione elevata
COUNTING B-FRAGMENTS
Taxa were scored based on how many different bivalve species they would be easily confused with if a hinge fragment were not present:
One: Shell structure and sculpture sufficient to confidently identify taxa
Two: Species easily confused with one other taxon
Three: Species easily confused with two other taxa
Four: Species easily confused with at least three other taxa
Brachidontes exustus
SPECIES FOUND AS HINGE FRAGMENTS
11/30 species (37%) found as hinge fragments were missing from the B-fragment-only portion of the sample.
Recognizability Score
Hing
e Fr
agm
ent C
ount
(n
=1,1
08)
11
2 3 4
10
100
1,000
x2 (2)
1,0000
x2 (2)
x4 (2)
x2 (2)
x2 (1) x3
x2
Timoclea grus (1)Crassinella lunulata (1)Parvilucina amianta (10)
Diplodonta punctata (3)Acar domingensis (1)Macrocallista nimbosa (1)
Abra aequalis (3)Nearomya floridana (3)Transennella stimpsoni (3)Noetia ponderosa
Semele proficula (1)
1
2
3
45/7 bivalves with recognizability scores of 3 or 4 are missing from the B-fragment-only sample.
8 of the missing species have very small adult shell sizes.
Species not found as B-fragments
1 10 100 1000 100001
10
100
1000
Hin
ge F
ragm
ent C
ount
(N=1
,108
)
B-Fragment Count (N=3,088)
Caloosa Shell Quarry Fort Thompson Bivalves
SPECIES MORE ABUNDANT AS HINGE FRAGMENTS
The three species found at least 3x more abundantly as hinge fragments than B-fragments are species with small adult body size.
P. nassula (13,80)
Mulinia (8,32)
P. multilineata(3,10)
Hin
ge F
ragm
ent C
ount
(N=1
,108
)
B-Fragment Count (N=3,088)1 10 100 1000 10000
1
10
100
1000
Caloosa Shell Quarry Fort Thompson Bivalves
SPECIES MORE ABUNDANT AS B-FRAGMENTS
Most of the species found at least 9x more abundantly as B-fragments than hinge fragments are (not surprisingly) fragile. They also lack large hinge teeth.
Ostreola (95,7)Brachidontes (56,6)
Argopecten (35, 2)Dosinia (17, 1)
Dosinia elegans is a large bivalve.
Recognizability Score
B-Fr
agm
ent C
ount
(n=3
,088
)
11
2 3 4
10
100
1,000
10,000
x2 (2)
Trachycardium egmontonium
SPECIES FOUND AS B-FRAGMENTS
19 of 22 species found in the B-fragments were also identified as hinge fragments within the same sample.
Two of the three species are large and relatively fragile compared to most FTT bivalves.
All three species are found in other FTT samples.
1
Chama congregata
1
Spisula solidissima
1
Trachycardium egmontonium
Caloosa Shell Quarry Fort Thompson Formation
BIAS IN THE B-FRAGMENT SUB-SAMPLE
Smaller bivalve species
Bivalve species that were less readily identifiable without an attached hinge fragments.
Easily fragmented bivalve species
Bivalve species with more readily identifiable shell structure
Larger bivalve species
500 1000 1500 2000 2500 3000 3500 400000
4
8
12
16
20
24
28
32
36
B-fragments
hinge fragmentsall fragments
RAREFIED DIVERSITY
All FTT samples
19
24
3230
Caloosa Shell Quarry Fort Thompson Bivalves
Specimens
Taxa
Hammer, Ø., Harper, D.A.T., Ryan, P.D. 2001. PAST: Paleontological statistics software package for education and data analysis. Palaeontologia Electronica 4(1): 9pp. http://palaeo-electronica.org/2001_1/past/issue1_01.htm
SPECIES FOUND AS FRAGMENTS
The non-hinge fragment portion of the sample contains only a sub-sample of the bivalve diversity.
Including all of the fragments in the count lowers the measured diversity.
Caloosa Shell Quarry Fort Thompson Bivalve Species Richness
This Study
12 bulk, 33 cm intervals of 4 sections
2 kg of sediment/sample processed
1
Portell et al. 1995
Portell, R.W., K.S. Schindler and D. Nichol. 1995. Biostratigraphy an paleoecology of the Pleistocene invertebrates from the Leisey Shell Pits, Hillsborough Country, Florida. Bulletin of the Florida Museum of National History 37 Pt. I: 127-164.
6 bulk, 1 m intervals of 3 sections
5-7 kg of sediment/sample processed
2Localities
Sampling
Processing
Sieve Size
Hunt and pick? No Yes
specimens >4 mm identified specimens >1 mm identified
45 species 49 species
3 species missing from Portell et al.’s list were very rare (12, 4, 3 specimens) in this study7 species missing from Portell et al.’s Fort Thompson list were found in lower strata
Species Richness:
35 species are found on both lists
10 species 14 speciesNot on other list:
2 species missing from this study’s Fort Thompson list were found in lower strata2 species from this study are too small to be retained on a 4 mm sieve. 10 species, including several large and easily identified species, were on Portell et al.’s list but not present in the samples of this locality from this study
< 0.1%