Population structure of Lepomis megalotis in seasonally fragmented streams: inferences from a nested cladistic analysis

J.W. Love1

C.M. Taylor1

A.P. Rooney2

M.L. Warren, Jr.3

1 Mississippi State University, Department of Biological Sciences2 U.S.D.A. Agricultural Research Service3 U.S.D.A. Forest Service, Oxford, MS

Objectives

• Identify population fragmentation for Lepomis megalotis (longear sunfish) in seasonally fragmented streams

• Characterize gene flow among fragmented subpopulations

Life History Characteristics• Gene flow influenced by dispersal capability (Zimmerman 1987)

• Limited dispersal (Hasler and Wisby 1954; Berra and Gunning 1972)

• Restricted movement paradigm (RMP; Gowan et al. 1994)

• Relatively high

immigration rate

among pools in study

area (I = 0.35; Taylor and

Warren 2001)

Lepomis megalotis (longear sunfish)

Turner Falls

Colorado River

Lake Sylvia

Possible Causes of Population Fragmentation

Study Area

• Identify population fragmentation– Fragmentation related to seasonal (i.e., local) and

permanent (i.e., regional) barriers to gene flow– Differentiation between subpopulations related to

stream distance between them– Differentiation related to extinction of rare

haplotypes (September sampling)

• Characterize gene flow among fragmented subpopulations– Overall pattern of restricted gene flow consistent

with the RMP

Objectives

Haplotype Determination: D-Loop, mtDNA

CAATTAAAGATTTTTTGGATTGCCCTATGAATTATTTGGAAAATGCCACAAATATTAAATATTTAGTTAGACTGTCAATTAAAGATTTTTTGGATTGCCCTATAAATTATTTGGAAAATGCCACAAATATTAAATATTTAGTAAGACTGTCGATTAAAGATTTTTTGGATTGCCCTATAAATTATTTGGAAAATGCCACAAATATTAAATATTTAGTTAGACTGTCGATTAAAGATTTTTTGGATTGCCCTATAAATTAATTGGAAAATGCCACAAATATTAAATATTTAGTAAGACTGTCGACTAAAGATTTTTTGGATTGCCCTATAAATTAATTGGAAAATGCCACAAATATTAAATATGTAGTAAGACTGTCAATTAAGGGTTCTTTAAATCACTCTATAAATTAATTAAAAAATACCACAAACACTAAACATATAATAAGATTATCAATTAAAGATTCTTTAAATTGCTCTACAAACTAATAAAAAAATATCACAAACACTAAACATATAATGAGACTATCAATTAAAGATTCTTTAAATCACTCTATAAATTAATCAAAAAATACTACAAACACTAAACATATAATAAAATTATGAATTAAAGATTCTTTAGATTACCCTATAAATTAATAAAAAAATACCACAAACACTAAACATATAATAAAACTGT

AGTTATAAATGGAATCCATAATATAATACAAAATTTAAAAATGATTAATATATAATGGTATGTCATCTGTCATCCTAAAAGAATAGTTTACAATCTAGTGGGATGAGGGAAGTTATAAATGGAATCCATAATATAATACAAAATTTAAAAATGATTAATATATAATGGTATGTCATCTGTCATCCTAAAAGAATAGTTTACAATCTAGTGGGATGAGGGAAGTTATAAATGGAATCCATAATATAATACAAAATTTAAAAATGATTAATATATAGTGGTATGTCATCTGTCATCCTAAAAGAATAGTCTCCAATCTAGTGGGATGAGGGAAGTTATAAATGGAATCCATAATATAATACAAAATTTAAAAATGATTAATATATAATGGTATGTCATCTGTCATCCTAAAAGAATAGTTTACAATCTAGTGGGATGAGGGAAGTTATAAATGGAATCCATAATATAATACAAAATTTAAAAATGATTAATATATAATGGTATGTCATCTGTCATCCTAAAAGAATAGTTTACAATCTAGTGGGATGAGGGAAAGCATAAACAAAATACATAATATAATACGAAACTTAAAAACAATTAGTCTATAACGACACACCATCCGCCATCCTACATGAGTAGCCTATATTCTAATAGGATGAAGGAGACCATAAACAAAATCCATAGTATCGTACAAAATTTAAAAACAATTAGTCCATAACGACACACCCTCCGCCATCCTAAATGAATAGCCTACAATCTAATGGGATGAAGGAAACCACAAACAAAATACATAATATAATACAAAATTTAAAAACAATTAATTCATAACAACACACCATCCACCATCCTAAATGAATAACCTATATTCTAATATGATGAAGAAGATCATAAACAAAATACATAGTATAATACAAAATTTAAAAACAATTAGTTTATAACAATACATCATCTGCCGTTCTAAAAAAACATCCCACACCCCAATAAAATAAAAAA

Sequence Determination: Unique Haplotypes

No Hierarchy % Var Φ-Statistic PAmong sites 4.53 0.0453 0.0198Within population 95.47 0.3744

2-region HierarchyBetween regions -1.32 ΦCT = -0.013 0.5918Among sites 5.27 ΦSC = 0.0520 0.0203within regionsWithin population 96.05 ΦST = 0.0394 0.0204

3-region HierarchyAmong regions -0.23 ΦCT = -0.0023 0.4743Among sites 4.72 ΦSC = 0.0471 0.0392within regionsWithin population 95.51 ΦST = 0.0448 0.0207

Population Fragmentation-AMOVA Results

Population Fragmentation-Isolation by Distance

Geographic Distance (km)0 25 50 75 100 125

Pai

rwis

e F

st

-0.06

-0.04

-0.02

0.00

0.02

0.04

0.06

0.08r2 = - 0.11P = 0.68

L. megalotisF. olivaceusI. punctatusE. whippleiL.

umbratalis

L. megalotisF. olivaceusE. whipplei

L. megalotisE. whipplei

Haplo AHaplo BHaplo CHaplo DHaplo E

Haplo AHaplo CHaplo E

Haplo AHaplo C

Extinction

Population Fragmentation-Extinction

Population Fragmentation-Nested Subsets

P [T < 14.35º] = 0.0375

Characterizing Fragmentation-Haplotype Network

Characterizing Fragmentation-

Table 3. Inferences suggested by Templeton (1998) for results from a nested cladistic analysis.These inferences are based on significance tests from Figure.

Clade Chain of inference InferenceHaplotypes nested in 1, 2, 11, 12 Contiguous range expansionClade 1-1One-step clades nested 1, 2, 11, 12 Contiguous range expansionin 2-1Two-step clades nested 1, 2, 3, 4, NO Restricted gene flow with in total cladogram isolation by distance

Nested Cladistic Analysis Results

• Subpopulations of L. megalotis are significantly differentiated, but among region differences were less important than among site differences

• Extinction processes influenced population fragmentation rather than geographic distance among sites

• While L. megalotis exhibits restricted gene flow, long-range movement is probable and may contribute to recolonization of extirpated subpopulations

Conclusions

• Bayesian analyses? – Corander et al. 2003• Bottleneck effects, particularly at a site? –

Luikart et al. 1998• Demographic history? – Skyline plots, Pybus et

al. 2000

Future Directions

AcknowledgementsU.S.D.A. Forest Service

Department of Biological Sciences (M.S.U.)

Tom McElroy (Forest Products-M.S.U.)Anna Chromiack (LSBI-M.S.U.)

Jim Grady (University of New Orleans) Karen Kandl (University of New Orleans)

Kristine Oswald (M.S.U.)Jill Arnold (U.S.D.A.)

Andy Sanders (M.S.U.)