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Niche specificity influences gene flow across fine‐scale habitat mosaics in Succulent Karoo plants
Author(s) -
Musker Seth D.,
Ellis Allan G.,
Schlebusch Stephen A.,
Verboom G. Anthony
Publication year - 2021
Publication title -
molecular ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.619
H-Index - 225
eISSN - 1365-294X
pISSN - 0962-1083
DOI - 10.1111/mec.15721
Subject(s) - biology , edaphic , gene flow , biological dispersal , ecology , niche , niche differentiation , population , ecological niche , habitat , biodiversity hotspot , spatial ecology , biodiversity , seed dispersal , genetic variation , gene , biochemistry , demography , sociology , soil water
Abstract While the tempo of diversification in biodiversity hotspots has received much attention, the spatial scale of diversification has often been overlooked. Addressing this deficiency requires understanding the drivers of population divergence and the spatial scales at which they operate in species‐rich clades and ecosystems. South Africa's Succulent Karoo (SK) hotspot provides an excellent system for such research, being both compact (ca. 110,000 km 2 ) and home to spectacular in‐situ radiations, such as the ruschioid Aizoaceae. Here we use GBS to document genetic structure in two co‐occurring ruschioid species, at both coarse (>10 km) and fine (<500 m) spatial scales. Where Ruschia burtoniae shows strong between‐population genetic differentiation and no gene flow, Conophytum calculus shows weak differentiation, with high levels of admixture suggesting recent or ongoing gene flow. Community analysis and transplant experiments reveal that R. burtoniae occupies a narrow, low‐pH edaphic niche, and at scales of a few hundred metres, areas of elevated genetic turnover correspond to patches of edaphically unsuitable habitat. In contrast, C. calculus occupies a broader niche and exhibits isolation‐by‐distance without a habitat effect. We suggest that edaphic specialisation, coupled with highly restricted seed and pollen dispersal in heterogeneous landscapes, has played a major role in driving rapid diversification at small spatial scales in this system. However, the contrasting patterns in our study species show that these factors do not influence all organisms uniformly, being strongly modulated by lineage‐specific traits that influence both the spatial scale of gene flow and habitat specificity.