TY - JOUR

T1 - Contrasting phylogeographic structures between freshwater lycopods and angiosperms in the British Isles

AU - Wood, Daniel P.

AU - Olofsson, Jill K.

AU - McKenzie, Scott W.

AU - Dunning, Luke T.

PY - 2018

Y1 - 2018

N2 - Aquatic plants face many novel challenges compared to their terrestrial counterparts. The habitat they occupy is typically highly fragmented, with isolated water bodies surrounded by swathes of “dry desert”. This can result in reduced gene flow, inbreeding, and potentially local extinction. The level of gene flow and degree of genetic structure in these species is also likely to be influenced by the mating system they adopt. To test this hypothesis we compare the phylogeographic structure of two freshwater plants in the British Isles, the largely clonal angiosperm Littorella uniflora, and the heterosporous lycopod Isoetes lacustris. We sampled both plants from lakes where they co-occur, and used restriction site-associated DNA sequencing (RAD-Seq) to infer their relationships. Genetic structure among lakes is higher in the angiosperm, which we associate with reduced sexual reproduction, and hence lower levels of gene flow between lakes. Furthermore, we found evidence of lineage-specific association to certain lake nutrient types in L. uniflora, which might result from environmental filtering of specific ecotypes. Overall, we conclude that the reproductive system of lycopods, which is less specialized to terrestrial conditions, provides an advantage following the secondary colonization of aquatic habitats by enabling frequent genetic exchanges between populations and potentially facilitating faster adaptation.

AB - Aquatic plants face many novel challenges compared to their terrestrial counterparts. The habitat they occupy is typically highly fragmented, with isolated water bodies surrounded by swathes of “dry desert”. This can result in reduced gene flow, inbreeding, and potentially local extinction. The level of gene flow and degree of genetic structure in these species is also likely to be influenced by the mating system they adopt. To test this hypothesis we compare the phylogeographic structure of two freshwater plants in the British Isles, the largely clonal angiosperm Littorella uniflora, and the heterosporous lycopod Isoetes lacustris. We sampled both plants from lakes where they co-occur, and used restriction site-associated DNA sequencing (RAD-Seq) to infer their relationships. Genetic structure among lakes is higher in the angiosperm, which we associate with reduced sexual reproduction, and hence lower levels of gene flow between lakes. Furthermore, we found evidence of lineage-specific association to certain lake nutrient types in L. uniflora, which might result from environmental filtering of specific ecotypes. Overall, we conclude that the reproductive system of lycopods, which is less specialized to terrestrial conditions, provides an advantage following the secondary colonization of aquatic habitats by enabling frequent genetic exchanges between populations and potentially facilitating faster adaptation.

KW - ecotype

KW - Isoetes

KW - Littorella

KW - macrophyte

KW - RAD-Seq

KW - reproductive system

KW - UK

U2 - 10.1080/23818107.2018.1505545

DO - 10.1080/23818107.2018.1505545

M3 - Journal article

AN - SCOPUS:85052078431

VL - 165

SP - 476

EP - 486

JO - Botany Letters

JF - Botany Letters

SN - 2381-8107

IS - 3-4

ER -