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Trumbo DR, Hardy BM, Crockett HJ, Muths E, Forester BR, Cheek RG, Zimmerman SJ, Corey-Rivas S, Bailey LL, Funk WC. Conservation genomics of an endangered montane amphibian reveals low population structure, low genomic diversity and selection pressure from disease. Mol Ecol 2023; 32:6777-6795. [PMID: 37864490 DOI: 10.1111/mec.17175] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Revised: 10/07/2023] [Accepted: 10/11/2023] [Indexed: 10/23/2023]
Abstract
Wildlife diseases are a major global threat to biodiversity. Boreal toads (Anaxyrus [Bufo] boreas) are a state-endangered species in the southern Rocky Mountains of Colorado and New Mexico, and a species of concern in Wyoming, largely due to lethal skin infections caused by the amphibian chytrid fungus Batrachochytrium dendrobatidis (Bd). We performed conservation and landscape genomic analyses using single nucleotide polymorphisms from double-digest, restriction site-associated DNA sequencing in combination with the development of the first boreal toad (and first North American toad) reference genome to investigate population structure, genomic diversity, landscape connectivity and adaptive divergence. Genomic diversity (π = 0.00034-0.00040) and effective population sizes (Ne = 8.9-38.4) were low, likely due to post-Pleistocene founder effects and Bd-related population crashes over the last three decades. Population structure was also low, likely due to formerly high connectivity among a higher density of geographically proximate populations. Boreal toad gene flow was facilitated by low precipitation, cold minimum temperatures, less tree canopy, low heat load and less urbanization. We found >8X more putatively adaptive loci related to Bd intensity than to all other environmental factors combined, and evidence for genes under selection related to immune response, heart development and regulation and skin function. These data suggest boreal toads in habitats with Bd have experienced stronger selection pressure from disease than from other, broad-scale environmental variations. These findings can be used by managers to conserve and recover the species through actions including reintroduction and supplementation of populations that have declined due to Bd.
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Affiliation(s)
- D R Trumbo
- Department of Biology, Colorado State University, Fort Collins, Colorado, USA
| | - B M Hardy
- Department of Biology, Colorado State University, Fort Collins, Colorado, USA
- Department of Fish, Wildlife and Conservation Biology, Colorado State University, Fort Collins, Colorado, USA
- Graduate Degree Program in Ecology, Colorado State University, Fort Collins, Colorado, USA
| | - H J Crockett
- Colorado Parks and Wildlife, Fort Collins, Colorado, USA
| | - E Muths
- U.S. Geological Survey, Fort Collins Science Center, Fort Collins, Colorado, USA
| | - B R Forester
- Department of Biology, Colorado State University, Fort Collins, Colorado, USA
| | - R G Cheek
- Department of Biology, Colorado State University, Fort Collins, Colorado, USA
- Graduate Degree Program in Ecology, Colorado State University, Fort Collins, Colorado, USA
| | - S J Zimmerman
- U.S. Geological Survey, Fort Collins Science Center, Fort Collins, Colorado, USA
| | - S Corey-Rivas
- Department of Biology, New Mexico Highlands University, Las Vegas, New Mexico, USA
| | - L L Bailey
- Department of Fish, Wildlife and Conservation Biology, Colorado State University, Fort Collins, Colorado, USA
- Graduate Degree Program in Ecology, Colorado State University, Fort Collins, Colorado, USA
| | - W C Funk
- Department of Biology, Colorado State University, Fort Collins, Colorado, USA
- Graduate Degree Program in Ecology, Colorado State University, Fort Collins, Colorado, USA
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Mensch EL, Kronenberger JA, Broder ED, Fitzpatrick SW, Funk WC, Angeloni LM. A potential role for immigrant reproductive behavior in the outcome of population augmentations. Anim Conserv 2019. [DOI: 10.1111/acv.12486] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- E. L. Mensch
- Department of Biology Colorado State University Fort Collins CO USA
| | - J. A. Kronenberger
- Department of Biology Colorado State University Fort Collins CO USA
- Graduate Degree Program in Ecology Colorado State University Fort Collins CO USA
| | - E. D. Broder
- Department of Biology Colorado State University Fort Collins CO USA
- Biology Department St. Ambrose University Davenport IA USA
| | - S. W. Fitzpatrick
- W.K. Kellogg Biological Station Department of Integrative Biology Michigan State University Hickory Corners MI USA
| | - W. C. Funk
- Department of Biology Colorado State University Fort Collins CO USA
- Graduate Degree Program in Ecology Colorado State University Fort Collins CO USA
| | - L. M. Angeloni
- Department of Biology Colorado State University Fort Collins CO USA
- Graduate Degree Program in Ecology Colorado State University Fort Collins CO USA
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Polato NR, Gray MM, Gill BA, Becker CG, Casner KL, Flecker AS, Kondratieff BC, Encalada AC, Poff NL, Funk WC, Zamudio KR. Genetic diversity and gene flow decline with elevation in montane mayflies. Heredity (Edinb) 2017; 119:107-116. [PMID: 28489073 DOI: 10.1038/hdy.2017.23] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2016] [Revised: 03/25/2017] [Accepted: 03/27/2017] [Indexed: 01/15/2023] Open
Abstract
Montane environments around the globe are biodiversity 'hotspots' and important reservoirs of genetic diversity. Montane species are also typically more vulnerable to environmental change than their low-elevation counterparts due to restricted ranges and dispersal limitations. Here we focus on two abundant congeneric mayflies (Baetis bicaudatus and B. tricaudatus) from montane streams over an elevation gradient spanning 1400 m. Using single-nucleotide polymorphism genotypes, we measured population diversity and vulnerability in these two species by: (i) describing genetic diversity and population structure across elevation gradients to identify mechanisms underlying diversification; (ii) performing spatially explicit landscape analyses to identify environmental drivers of differentiation; and (iii) identifying outlier loci hypothesized to underlie adaptive divergence. Differences in the extent of population structure in these species were evident depending upon their position along the elevation gradient. Heterozygosity, effective population sizes and gene flow all declined with increasing elevation, resulting in substantial population structure in the higher elevation species (B. bicaudatus). At lower elevations, populations of both species are more genetically similar, indicating ongoing gene flow. Isolation by distance was detected at lower elevations only, whereas landscape barriers better predicted genetic distance at higher elevations. At higher elevations, dispersal was restricted due to landscape effects, resulting in greater population isolation. Our results demonstrate differentiation over small spatial scales along an elevation gradient, and highlight the importance of preserving genetic diversity in more isolated high-elevation populations.
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Affiliation(s)
- N R Polato
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY, USA
| | - M M Gray
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY, USA
| | - B A Gill
- Department of Biology, Colorado State University, Fort Collins, Colorado, USA
| | - C G Becker
- Departamento de Zoologia, Universidade Estadual Paulista, Rio Claro, Brazil
| | - K L Casner
- Department of Biology, Colorado State University, Fort Collins, Colorado, USA
| | - A S Flecker
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY, USA
| | - B C Kondratieff
- Department of Biology, Colorado State University, Fort Collins, Colorado, USA
| | - A C Encalada
- Colegio de Ciencias Biológicas y Ambientales, Universidad San Francisco de Quito, Quito, Ecuador
| | - N L Poff
- Department of Biology, Colorado State University, Fort Collins, Colorado, USA.,Institute of Applied Ecology, University of Canberra, ACT 2617, Australia
| | - W C Funk
- Department of Biology, Colorado State University, Fort Collins, Colorado, USA
| | - K R Zamudio
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY, USA
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Langin KM, Sillett TS, Funk WC, Morrison SA, Ghalambor CK. Partial support for the central-marginal hypothesis within a population: reduced genetic diversity but not increased differentiation at the range edge of an island endemic bird. Heredity (Edinb) 2017; 119:8-15. [PMID: 28327578 DOI: 10.1038/hdy.2017.10] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2016] [Revised: 11/30/2016] [Accepted: 01/22/2017] [Indexed: 11/09/2022] Open
Abstract
Large-scale population comparisons have contributed to our understanding of the evolution of geographic range limits and species boundaries, as well as the conservation value of populations at range margins. The central-marginal hypothesis (CMH) predicts a decline in genetic diversity and an increase in genetic differentiation toward the periphery of species' ranges due to spatial variation in genetic drift and gene flow. Empirical studies on a diverse array of taxa have demonstrated support for the CMH. However, nearly all such studies come from widely distributed species, and have not considered if the same processes can be scaled down to single populations. Here, we test the CMH on a species composed of a single population: the Island Scrub-Jay (Aphelocoma insularis), endemic to a 250 km2 island. We examined microsatellite data from a quarter of the total population and found that homozygosity increased toward the island's periphery. However, peripheral portions of the island did not exhibit higher genetic differentiation. Simulations revealed that highly localized dispersal and small total population size, but not spatial variation in population density, were critical for generating fine-scale variation in homozygosity. Collectively, these results demonstrate that microevolutionary processes driving spatial variation in genetic diversity among populations can also be important for generating spatial variation in genetic diversity within populations.
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Affiliation(s)
- K M Langin
- Department of Biology and Graduate Degree Program in Ecology, Colorado State University, Fort Collins, CO, USA
| | - T S Sillett
- Migratory Bird Center, Smithsonian Conservation Biology Institute, National Zoological Park, Washington, DC, USA
| | - W C Funk
- Department of Biology and Graduate Degree Program in Ecology, Colorado State University, Fort Collins, CO, USA
| | | | - C K Ghalambor
- Department of Biology and Graduate Degree Program in Ecology, Colorado State University, Fort Collins, CO, USA
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Kronenberger JA, Fitzpatrick SW, Angeloni LM, Broder ED, Ruell EW, Funk WC. Playing God with guppies - informing tough conservation decisions using a model experimental system. Anim Conserv 2017. [DOI: 10.1111/acv.12341] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- J. A. Kronenberger
- Department of Biology; Colorado State University; Fort Collins CO USA
- Graduate Degree Program in Ecology; Colorado State University; Fort Collins CO USA
| | - S. W. Fitzpatrick
- Kellogg Biological Station; Department of Integrative Biology; Michigan State University; Hickory Corners MI USA
| | - L. M. Angeloni
- Department of Biology; Colorado State University; Fort Collins CO USA
- Graduate Degree Program in Ecology; Colorado State University; Fort Collins CO USA
| | - E. D. Broder
- Interdisciplinary Research Incubator for the Study of (in)Equality; University of Denver; Denver CO USA
| | - E. W. Ruell
- Department of Biology; Colorado State University; Fort Collins CO USA
| | - W. C. Funk
- Department of Biology; Colorado State University; Fort Collins CO USA
- Graduate Degree Program in Ecology; Colorado State University; Fort Collins CO USA
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Gill BA, Kondratieff BC, Casner KL, Encalada AC, Flecker AS, Gannon DG, Ghalambor CK, Guayasamin JM, Poff NL, Simmons MP, Thomas SA, Zamudio KR, Funk WC. Cryptic species diversity reveals biogeographic support for the 'mountain passes are higher in the tropics' hypothesis. Proc Biol Sci 2016; 283:20160553. [PMID: 27306051 PMCID: PMC4920318 DOI: 10.1098/rspb.2016.0553] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2016] [Accepted: 05/18/2016] [Indexed: 01/30/2023] Open
Abstract
The 'mountain passes are higher in the tropics' (MPHT) hypothesis posits that reduced climate variability at low latitudes should select for narrower thermal tolerances, lower dispersal and smaller elevational ranges compared with higher latitudes. These latitudinal differences could increase species richness at low latitudes, but that increase may be largely cryptic, because physiological and dispersal traits isolating populations might not correspond to morphological differences. Yet previous tests of the MPHT hypothesis have not addressed cryptic diversity. We use integrative taxonomy, combining morphology (6136 specimens) and DNA barcoding (1832 specimens) to compare the species richness, cryptic diversity and elevational ranges of mayflies (Ephemeroptera) in the Rocky Mountains (Colorado; approx. 40°N) and the Andes (Ecuador; approx. 0°). We find higher species richness and smaller elevational ranges in Ecuador than Colorado, but only after quantifying and accounting for cryptic diversity. The opposite pattern is found when comparing diversity based on morphology alone, underscoring the importance of uncovering cryptic species to understand global biodiversity patterns.
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Affiliation(s)
- B A Gill
- Department of Biology, Colorado State University, Fort Collins, CO 80523, USA Graduate Degree Program in Ecology, Colorado State University, Fort Collins, CO 80523, USA
| | - B C Kondratieff
- Graduate Degree Program in Ecology, Colorado State University, Fort Collins, CO 80523, USA Department of Bioagricultural Sciences and Pest Management, Colorado State University, Fort Collins, CO 80523, USA
| | - K L Casner
- Department of Biology, Colorado State University, Fort Collins, CO 80523, USA
| | - A C Encalada
- Colegio de Ciencias Biológicas y Ambientales, Universidad San Francisco de Quito, Diego de Robles y Vía Interoceánica, 17-1200-841 Quito, Ecuador
| | - A S Flecker
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853, USA
| | - D G Gannon
- Department of Biology, Colorado State University, Fort Collins, CO 80523, USA
| | - C K Ghalambor
- Department of Biology, Colorado State University, Fort Collins, CO 80523, USA Graduate Degree Program in Ecology, Colorado State University, Fort Collins, CO 80523, USA
| | - J M Guayasamin
- Colegio de Ciencias Biológicas y Ambientales, Universidad San Francisco de Quito, Diego de Robles y Vía Interoceánica, 17-1200-841 Quito, Ecuador Centro de Investigación de la Biodiversidad y Cambio Climático, Ingeniería en Biodiversidad y Recursos Genéticos, Facultad de Ciencias de Medio Ambiente, Universidad Tecnológica Indoamérica, Calle Machala y Sabanilla, Quito, Ecuador
| | - N L Poff
- Department of Biology, Colorado State University, Fort Collins, CO 80523, USA Graduate Degree Program in Ecology, Colorado State University, Fort Collins, CO 80523, USA
| | - M P Simmons
- Department of Biology, Colorado State University, Fort Collins, CO 80523, USA
| | - S A Thomas
- School of Natural Resources, University of Nebraska, Lincoln, NE 68583, USA
| | - K R Zamudio
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853, USA
| | - W C Funk
- Department of Biology, Colorado State University, Fort Collins, CO 80523, USA Graduate Degree Program in Ecology, Colorado State University, Fort Collins, CO 80523, USA
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Kronenberger JA, Funk WC, Smith JW, Fitzpatrick SW, Angeloni LM, Broder ED, Ruell EW. Testing the demographic effects of divergent immigrants on small populations of Trinidadian guppies. Anim Conserv 2016. [DOI: 10.1111/acv.12286] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Affiliation(s)
- J. A. Kronenberger
- Department of Biology Colorado State University Fort Collins CO USA
- Graduate Degree Program in Ecology Colorado State University Fort Collins CO USA
| | - W. C. Funk
- Department of Biology Colorado State University Fort Collins CO USA
- Graduate Degree Program in Ecology Colorado State University Fort Collins CO USA
| | - J. W. Smith
- Department of Biology Colorado State University Fort Collins CO USA
| | | | - L. M. Angeloni
- Department of Biology Colorado State University Fort Collins CO USA
- Graduate Degree Program in Ecology Colorado State University Fort Collins CO USA
| | - E. D. Broder
- Department of Biology Colorado State University Fort Collins CO USA
- Graduate Degree Program in Ecology Colorado State University Fort Collins CO USA
| | - E. W. Ruell
- Department of Biology Colorado State University Fort Collins CO USA
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Funk WC, Murphy MA, Hoke KL, Muths E, Amburgey SM, Lemmon EM, Lemmon AR. Elevational speciation in action? Restricted gene flow associated with adaptive divergence across an altitudinal gradient. J Evol Biol 2015; 29:241-52. [DOI: 10.1111/jeb.12760] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2015] [Revised: 08/28/2015] [Accepted: 09/08/2015] [Indexed: 01/15/2023]
Affiliation(s)
- W. C. Funk
- Department of Biology Colorado State University Fort Collins CO USA
- Graduate Degree Program in Ecology Colorado State University Fort Collins CO USA
| | - M. A. Murphy
- Department of Ecosystem Science and Management University of Wyoming Laramie WY USA
- Program in Ecology University of Wyoming Laramie WY USA
| | - K. L. Hoke
- Department of Biology Colorado State University Fort Collins CO USA
| | - E. Muths
- U.S. Geological Survey Fort Collins Science Center Fort Collins CO USA
| | - S. M. Amburgey
- Department of Ecosystem Science and Management Pennsylvania State University University Park PA USA
- Intercollege Graduate Degree Program in Ecology Pennsylvania State University University Park PA USA
| | - E. M. Lemmon
- Department of Biology Florida State University Tallahassee FL USA
| | - A. R. Lemmon
- Department of Scientific Computing Florida State University Tallahassee FL USA
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Fitzpatrick SW, Gerberich JC, Kronenberger JA, Angeloni LM, Funk WC. Locally adapted traits maintained in the face of high gene flow. Ecol Lett 2014; 18:37-47. [PMID: 25363522 DOI: 10.1111/ele.12388] [Citation(s) in RCA: 73] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2014] [Revised: 06/06/2014] [Accepted: 10/01/2014] [Indexed: 11/26/2022]
Abstract
Gene flow between phenotypically divergent populations can disrupt local adaptation or, alternatively, may stimulate adaptive evolution by increasing genetic variation. We capitalised on historical Trinidadian guppy transplant experiments to test the phenotypic effects of increased gene flow caused by replicated introductions of adaptively divergent guppies, which were translocated from high- to low-predation environments. We sampled two native populations prior to the onset of gene flow, six historic introduction sites, introduction sources and multiple downstream points in each basin. Extensive gene flow from introductions occurred in all streams, yet adaptive phenotypic divergence across a gradient in predation level was maintained. Descendants of guppies from a high-predation source site showed high phenotypic similarity with native low-predation guppies in as few as ~12 generations after gene flow, likely through a combination of adaptive evolution and phenotypic plasticity. Our results demonstrate that locally adapted phenotypes can be maintained despite extensive gene flow from divergent populations.
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Affiliation(s)
- S W Fitzpatrick
- Department of Biology, Colorado State University, 1878 Campus Delivery, Fort Collins, CO, 80523, USA
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Fitzpatrick SW, Crockett H, Funk WC. Water availability strongly impacts population genetic patterns of an imperiled Great Plains endemic fish. CONSERV GENET 2014. [DOI: 10.1007/s10592-014-0577-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Trillo PA, Athanas KA, Goldhill DH, Hoke KL, Funk WC. The influence of geographic heterogeneity in predation pressure on sexual signal divergence in an Amazonian frog species complex. J Evol Biol 2012. [DOI: 10.1111/jeb.12041] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- P. A. Trillo
- Department of Biology; Colorado State University; Fort Collins CO USA
- Museo de Historia Natural; Universidad Nacional Mayor de San Marcos; Jesus María Lima Peru
| | - K. A. Athanas
- Department of Biology; Colorado State University; Fort Collins CO USA
| | - D. H. Goldhill
- Department of Ecology and Evolutionary Biology; Yale University; New Haven CT USA
| | - K. L. Hoke
- Department of Biology; Colorado State University; Fort Collins CO USA
| | - W. C. Funk
- Department of Biology; Colorado State University; Fort Collins CO USA
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12
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Affiliation(s)
- C D Cadena
- Laboratorio de Biología Evolutiva de Vertebrados, Departamento de Ciencias Biológicas, Universidad de los Andes, Bogotá, Colombia.
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Funk WC, Tyburczy JA, Knudsen KL, Lindner KR, Allendorf FW. Genetic basis of variation in morphological and life-history traits of a wild population of pink salmon. ACTA ACUST UNITED AC 2004; 96:24-31. [PMID: 15598713 DOI: 10.1093/jhered/esi009] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
Understanding the genetic basis of phenotypic variation is essential for predicting the direction and rate of phenotypic evolution. We estimated heritabilities and genetic correlations of morphological (fork length, pectoral and pelvic fin ray counts, and gill arch raker counts) and life-history (egg number and individual egg weight) traits of pink salmon (Oncorhynchus gorbuscha) from Likes Creek, Alaska, in order to characterize the genetic basis of phenotypic variation in this species. Families were created from wild-caught adults, raised to the fry stage in the lab, released into the wild, and caught as returning adults and assigned to families using microsatellite loci and a growth hormone locus. Morphological traits were all moderately to highly heritable, but egg number and egg weight were not heritable, suggesting that past selection has eliminated additive genetic variation in egg number and egg weight or that there is high environmental variance in these traits. Genetic correlations were similar for nonadjacent morphological traits and adjacent traits. Genetic correlations predicted phenotypic correlations fairly accurately, but some pairs of traits with low genetic correlations had high phenotypic correlations, and vice versa, emphasizing the need to use caution when using phenotypic correlations as indices of genetic correlations. This is one of only a handful of studies to estimate heritabilities and genetic correlations for a wild population.
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Affiliation(s)
- W C Funk
- Division of Biological Sciences, University of Montana, Missoula, MT 59812-4824, USA.
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Abstract
The effective population sizes (Ne) of six populations of the long-toed salamander (Ambystoma macrodactylum) from Montana and Idaho, USA were estimated from allozyme data from samples collected in 1978, 1996 and 1997 using the temporal allele frequency method. Five of the six estimates ranged from 23 to 207 (mean = 123 +/- 79); one estimate was indistinguishable from infinity. In order to infer the actual Ne of salamander populations, we compared the frequency distribution of our observed Ne estimates with distributions obtained from simulated populations of known Ne. Our observed Ne estimate distribution was consistent with distributions from simulated populations with Ne values of 10, 25, and 50, suggesting an actual Ne for each of the six salamander populations of less than 100. This Ne estimate agrees with most other Ne estimates for amphibians. We conclude by discussing the conservation implications of small Ne values in amphibians in the context of increasing isolation of populations due to habitat fragmentation.
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Affiliation(s)
- W C Funk
- Division of Biological Sciences, University of Montana,, Missoula 59812, USA.
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Abstract
In cleaving Xenopus eggs, exposure to nocodazole or cold shock prevents the addition of new plasma membrane to the cleavage plane and causes furrows to recede, suggesting a specific role for microtubules in cytokinesis. Whole-mount confocal immunocytochemistry reveals a ring of radially arranged, acetylated microtubule bundles at the base of all advancing cleavage furrows, from the first cleavage through the midblastula stage. We hypothesize that this novel microtubular structure is involved in transporting maternal stores of membrane in the subcortex to a site of membrane addition near the leading edge of the furrow.
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Affiliation(s)
- M V Danilchik
- Department of Biological Structure and Function, Oregon Health Sciences University, Portland, Oregon 97201-3097, USA
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