engleski

The story of Proasellus (Isopoda, Crustacea) - cave colonization ensured by the plastic response?

Some taxa successfully adapted to caves across diverse geographic and temporal scales, while others have a few or no cave-dwelling representatives. This implies that groups that gave rise to numerous cave species have some preadaptations which allow them to colonize, survive, and eventually fully adapt to the subterranean environment. We ask whether phenotypic plasticity could be an underlying mechanism that enables successful cave colonization in the early stages as it was shown for the cavefish Astyanax mexicanus? Genus Proasellus has invaded caves multiple times independently. As a model system, we selected a widespread surface species P. coxalis which is also known to form cave populations. To understand which adaptations evolve in subterranean species in this genus, we used a closely related cave species P. anophtalmus. We exposed one randomly selected group of both species to complete darkness (DD) and the other group to a normal light-dark photoperiod (LD) as controls. After four months in the experiment, DD and LD cohorts differ in gene expression, but P. coxalis showed a more pronounced plastic response (3024 DEGs) compared to P. anophtalmus (491 DEGs). At the phenotypic level, differences between DD and LD P. coxalis (first generation hatched in the experiment) indicated better general fitness in DD conditions (growth rate, fecundity, survival) while some traits (body pigmentation, metabolic rate) changed in the nonadaptive direction. Our results indicate that phenotypic plasticity may be a general mechanism for adaptation to the darkness of caves.

cave colonization ; phenotypic plasticity ; Proasellus

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