Comparative population genetic structure in a plant-pollinator/seed predator system

Abstract

Comparative analyses of spatial genetic structure of populations of plants and the insects they interact with provide an indication of how gene flow, natural selection and genetic drift may jointly influence the distribution of genetic variation and potential for local co-adaptation for interacting species. Here, we analysed the spatial scale of genetic structure within and among nine populations of an interacting species pair, the white campion Silene latifolia and the moth Hadena bicruris, along a latitudinal gradient across Northern/Central Europe. This dioecious, short-lived perennial plant inhabits patchy, often disturbed environments. The moth H. bicruris acts both as its pollinator and specialist seed predator that reproduces by laying eggs in S. latifolia flowers. We used nine microsatellite markers for S. latifolia and eight newly developed markers for H. bicruris. We found high levels of inbreeding in most populations of both plant and pollinator/seed predator. Among populations, significant genetic structure was observed for S. latifolia but not for its pollinator/seed predator, suggesting that despite migration among populations of H. bicruris, pollen is not, or only rarely, carried over between populations, thus maintaining genetic structure among plant populations. There was a weak positive correlation between genetic distances of S. latifolia and H. bicruris. These results indicate that while significant structure of S. latifolia populations creates the potential for differentiation at traits relevant for the interaction with the pollinator/seed predator, substantial gene flow in H. bicruris may counteract this process in at least some populations.

Contrasting genetic responses to population fragmentation in a coevolving fig and fig wasp across a mainland–island archipelago

“…Magalhaes et al . () similarly detected no significant correlation between the genetic distances of Silene latifolia and its pollinator, the moth Hadena bicruris . Nevertheless, populations of intimately interacting species do sometimes show similar patterns (e.g.…”

Strong phylogeographic co‐structure between the anther‐smut fungus and its white campion host

“…It would be interesting in future studies to also assess the genetic co‐structure between the plants the fungus and the pollinators. In fact, a previous work at a smaller geographical scale found a correlation between among‐population genetic distances of S. latifolia and Hadena biscuris, a pollinator and seed‐eater of the plant (Magalhaes et al ., ).…”

“…Finally, the mating systems are important life‐history traits that may explain lower levels of gene flow among populations in the fungus than in the plant. Although F IS values obtained here and previously suggest that some inbreeding occurs in this dioecious plant (Delmotte et al ., ; Magalhaes et al ., ; Keller et al ., ) despite dioecy and inbreeding depression (Teixeira et al ., ), the fungus has a much more closed mating system, being highly selfing (Delmotte et al ., ; Hood & Antonovics, ; Giraud, ; Giraud et al ., ). Therefore, it may well be that the stronger subdivision in the anther‐smut fungus reflects fragmented ranges in southern refugia and/or more northern refugia, but that the higher level of gene flow in the plant has erased their footprints by homogenizing allele frequencies.…”

Cost limitation through constrained oviposition site in a plant‐pollinator/seed predator mutualism

“…In addition, comparative phenotyping of plant and moth in the wild would be highly valuable to understand the degree of trait matching and its consequences because H. bicruris moves extensively among S. latifolia populations (Magalhaes et al . ) and consequently, female plants interact with moths of different origin and presumably with variable ovipositor lengths.…”

“…and Supplementary Method S1; see also Magalhaes et al . ) and exposed them in a common garden located at the southernmost latitude of the sampling area (Fig. ).…”