Does life in unstable environments favour facultative selfing? A case study in the freshwater snail Drepanotrema depressissimum (Basommatophora: Planorbidae)

Abstract

One of the main advantages of self-fertilization is to provide reproductive assurance when pollen or mates are scarce. In plants, partial or facultative selfing limits the risk of pollination failure. In preferentially outcrossing species, this may result in mixedmating. In hermaphroditic animals, recent studies suggest that mixed mating might be much rarer than in plants. However more studies are required to substantiate this claim, especially focusing on species whose lifestyle entails a high potential benefit of reproductive assurance via selfing. We studied a hermaphroditic snail, Drepanotrema depressissimum, which inhabits very unstable and fragmented freshwater habitats. Individuals often have to recolonize newly refilled ponds after long droughts, a situation of low population density and hence low mate availability in which selfing could be an advantage. We estimated selfing rates in natural populations from Guadeloupe (Lesser Antilles), and used laboratory experiments to characterize the reproductive behaviour and success of individuals with or without mates. We detected no sign of selfing in natural populations. Even when given no other option, isolated individuals were extremely reluctant to self. They produced either no or very small clutches, and in the latter case initiated egg-laying later than non-isolated individuals. Self-fertilized clutches suffered near-total (98%) inbreeding depression at the juvenile stage. The example of D. depressissimum therefore shows that a species can overcome periods of mate shortage and habitat instability without the potential to rely on facultative selfing. We hypothesize that metapopulation persistence in this landscape is probably related to a form of dormancy (aestivation in dry ground) rather than to recolonization by rare immigrants and reproductive assurance.Electronic supplementary material The online version of this article (

Variation in habitat connectivity generates positive correlations between species and genetic diversity in a metacommunity

“…; Lamy et al . ). At each site, eight to 32 snails (mean = 21.77 ± 7.78) were collected corresponding to a total of 1633 individuals (902 and 731 in 32 and 43 sites in D. depressissimum and A. marmorata, respectively; previous rarefaction analysis suggested that sampling ten to 15 individuals per population for both species allows to capture difference in GD).…”

“…2000) but also a few small gullies (which consist of succession of ponds occasionally connected by water flow) and swamp grasslands connected to mangroves (Bruyere & Questel ; Pointier & David ; Lamy et al . ,b, ). Some of these sites are permanent, but many ponds completely dry out, either yearly or more irregularly, during the dry season (i.e.…”

“…A. marmorata (Gastropoda: Basommatophora: Physidae) is the most represented species in the metacommunity (mean site occupancy over the 11 surveyed years: 71%) and mostly reproduces through selfing (Dubois et al 2008;Escobar et al 2011). D. depressissimum (Gastropoda: Basommatophora: Planorbidae) is the second most represented species in the metacommunity (mean site occupancy: 58%) and mostly reproduces through outcrossing (Nicot et al 2009;Lamy et al 2012b). At each site, eight to 32 snails (mean = 21.77 AE 7.78) were collected corresponding to a total of 1633 individuals (902 and 731 in 32 and 43 sites in D. depressissimum and A. marmorata, respectively; previous rarefaction analysis suggested that sampling ten to 15 individuals per population for both species allows to capture difference in GD).…”

Occurrence, costs and heritability of delayed selfing in a free‐living flatworm

“…These observations suggest M. hystrix may in fact frequently encounter environmental conditions of high mate availability and intense sperm competition, coupled with an ability to deal with periods of low mate availability through the delayed selfing behaviour we demonstrate in this study (c.f. for example Lamy et al, 2012).…”

Testing metapopulation dynamics using genetic, demographic and ecological data

“…The method assumes an infinitely large source population providing immigrants to the focal population in which N e and m are estimated. Generation time was fixed at two months (based on laboratory cultures, Lamy et al. 2012), and the maximum N e was set at 4000.…”