TY - JOUR

T1 - Effects of dispersal strategy and migration history on genetic diversity and population structure of Antarctic lichens

AU - Lagostina, Elisa

AU - Andreev, Mikhail

AU - Dal Grande, Francesco

AU - Grewe, Felix

AU - Lorenz, Aline

AU - Lumbsch, H. Thorsten

AU - Rozzi, Ricardo

AU - Ruprecht, Ulrike

AU - Sancho, Leopoldo García

AU - Søchting, Ulrik

AU - Scur, Mayara

AU - Wirtz, Nora

AU - Printzen, Christian

PY - 2021

Y1 - 2021

N2 - Aim: The homogenisation of historically isolated gene pools has been recognised as one of the most serious conservation problems in the Antarctic. Lichens are the dominant components of terrestrial biotas in the Antarctic and in high mountain ranges of southern South America. We study the effects of dispersal strategy and migration history on their genetic structure to better understand the importance of these processes and their interplay in shaping population structure as well as their relevance for conservation. Location: Maritime Antarctic and southern South America. Methods: Populations of three fruticose lichen species, Usnea aurantiacoatra, U. antarctica and Cetraria aculeata, were collected in different localities in the Maritime Antarctic and southern South America. Usnea aurantiacoatra reproduces sexually by ascospores, whereas the other two species mostly disperse asexually by symbiotic diaspores. Samples were genotyped at 8–22 microsatellite loci. Different diversity and variance metrics, Bayesian cluster analyses and Discriminant Analysis of Principal Components (DAPC) were used to study population genetic structure. Historical migration patterns between southern South America and the Antarctic were investigated for U. aurantiacoatra and C. aculeata by approximate Bayesian computation (ABC). Results: The two vegetative species display lower levels of genetic diversity than U. aurantiacoatra. Antarctic populations of C. aculeata and South American populations of U. aurantiacoatra display much stronger genetic differentiation than their respective counterparts on the opposite side of the Drake Passage. Usnea antarctica was not found in South America but shows comparably low levels of genetic differentiation in Antarctica as those revealed for U. aurantiacoatra. Phylogeographic histories of lichens in the region differ strongly with recent colonisation in some instances and potential in situ persistence during Last Glacial Maximum (LGM) in others. Patterns of genetic diversity indicate the presence of glacial refugia near Navarino Island (South America) and in the South Shetland Islands. ABC analyses suggest that C. aculeata colonised the Antarctic from Patagonia after the LGM. Results for U. aurantiacoatra are ambiguous, indicating a more complex population history than expressed in the simplified scenarios. Main Conclusions: Mode of propagation affects levels of genetic diversity, but the location of glacial refugia and postglacial colonisation better explains the diversity patterns displayed by each species. We found evidence for glacial in situ survival of U. aurantiacoatra on both sides of the Drake Passage and postglacial colonisation of Antarctica from South America by C. aculeata. Maintaining the strong genetic differentiation of Antarctic populations of C. aculeata requires strict conservation measures, whereas populations of U. aurantiacoatra are exposed to a much lower risk due to their higher diversity and connectivity.

AB - Aim: The homogenisation of historically isolated gene pools has been recognised as one of the most serious conservation problems in the Antarctic. Lichens are the dominant components of terrestrial biotas in the Antarctic and in high mountain ranges of southern South America. We study the effects of dispersal strategy and migration history on their genetic structure to better understand the importance of these processes and their interplay in shaping population structure as well as their relevance for conservation. Location: Maritime Antarctic and southern South America. Methods: Populations of three fruticose lichen species, Usnea aurantiacoatra, U. antarctica and Cetraria aculeata, were collected in different localities in the Maritime Antarctic and southern South America. Usnea aurantiacoatra reproduces sexually by ascospores, whereas the other two species mostly disperse asexually by symbiotic diaspores. Samples were genotyped at 8–22 microsatellite loci. Different diversity and variance metrics, Bayesian cluster analyses and Discriminant Analysis of Principal Components (DAPC) were used to study population genetic structure. Historical migration patterns between southern South America and the Antarctic were investigated for U. aurantiacoatra and C. aculeata by approximate Bayesian computation (ABC). Results: The two vegetative species display lower levels of genetic diversity than U. aurantiacoatra. Antarctic populations of C. aculeata and South American populations of U. aurantiacoatra display much stronger genetic differentiation than their respective counterparts on the opposite side of the Drake Passage. Usnea antarctica was not found in South America but shows comparably low levels of genetic differentiation in Antarctica as those revealed for U. aurantiacoatra. Phylogeographic histories of lichens in the region differ strongly with recent colonisation in some instances and potential in situ persistence during Last Glacial Maximum (LGM) in others. Patterns of genetic diversity indicate the presence of glacial refugia near Navarino Island (South America) and in the South Shetland Islands. ABC analyses suggest that C. aculeata colonised the Antarctic from Patagonia after the LGM. Results for U. aurantiacoatra are ambiguous, indicating a more complex population history than expressed in the simplified scenarios. Main Conclusions: Mode of propagation affects levels of genetic diversity, but the location of glacial refugia and postglacial colonisation better explains the diversity patterns displayed by each species. We found evidence for glacial in situ survival of U. aurantiacoatra on both sides of the Drake Passage and postglacial colonisation of Antarctica from South America by C. aculeata. Maintaining the strong genetic differentiation of Antarctic populations of C. aculeata requires strict conservation measures, whereas populations of U. aurantiacoatra are exposed to a much lower risk due to their higher diversity and connectivity.

KW - approximate Bayesian computation

KW - biodiversity

KW - Cetraria aculeata

KW - climate change

KW - conservation

KW - microsatellites

KW - Parmeliaceae

KW - U. aurantiacoatra

KW - Usnea antarctica

U2 - 10.1111/jbi.14101

DO - 10.1111/jbi.14101

M3 - Journal article

AN - SCOPUS:85102863358

VL - 48

SP - 1635

EP - 1653

JO - Journal of Biogeography

JF - Journal of Biogeography

SN - 0305-0270

IS - 7

ER -