Environmental variation and life-history evolution : experiments on Caenorhabditis remanei

摘要: Organisms are constantly altering their phenotypes in response to changing environments. Many of these differences known be due genetic changes. However, some the between individuals will phenotypic plasticity. Phenotypic plasticity is property a given genotype produce different distinct environments (Pigliucci 2001). can adaptive and may provide with means thrive across wide range Thus it represents one solution surviving variable environment. Maintaining high population variance also recognized as enabling respond Both constitute responses environments, but rely on quite mechanisms. The purpose my project examine by what means, history influence responsiveness populations environmental change. In order approach this question I used model species (Caenorhabditis remanei) selection experiments laboratory. Caenorhabditis widely research, for instance, study mechanisms affecting gene expression effects individual’s phenotype. Despite this, we have limited understanding importance factors that control demography laboratory or nature. Particularly, other nematode than C. elegans has until very recently been ignored. Thus, described basic remanei cultured under standard conditions. compared life two geographically distant Differences were expected present consequence local adaptation My results show short generation time, surprisingly similar time elegans. Moreover, found there was little difference populations. Between individuals, variance, which would partially result diversity within population. C. morphologically indistinguishable. they differ reproductive biology; former facutatively reproduces selfing, whereas latter only progeny crossing (hermaphroditism gonochorism, respectively). Sexual conflict, strategies males females, previously identified soil evidence sexual conflict lacking gonochoristic nematode. conducted an experiment effect number females’ fecundity survival rate. increasing increases female fecundity. suggesting females sperm limited. threshold, further increase reduced These agreement theory conflict. Environmentally-dependent traits universally common species. For remanei, life-history such environmentally dependent, dependencies remain poorly understood. improve our remanei’s environments; exposed three worms (two wild type isolates half-diall cross them) six temperatures assessed response. half-sib breeding design estimate gene-environment interaction all traits. composition. optimal at 17 °C, higher growth temperature established Although 5 30 °C significantly fecundity, still permissive individuals. Not plastic adaptive. It recognised heterogeneous select manipulate levels, maintained 50 generations environments: constant predictably fluctuating temperature. Life-history components quantified times during course (generation 1, 20 50). If adaptive, could strong After experiment, comparisons evolved allowed me quantify how evolutionary pressures shaped strains’ history, depended likely levels (i.e. pure strains hybrid). both changes schedules. did not detect significant lifetime after showed early This shift parameters shows pressures. evolution. In theory, wider ecological breath no each environment, assayed assess whether (e.g. tolerance temperature). Higher tolerance) environment more stable from stressful conditions, while successfully selected low plasticity. Adaptive fitness because expresses “matching” phenotype according cues. machinery match disadvantage less when changing. linked reallocation resources maintenance cellular enables production matching test hypothesis, translocated translocation, moved back into reproduced before took place (reared environment). strongly supports idea turn individual “The Jack trades, Master none”.