Differential Morphology and Jumping Performance of Newly Metamorphosed Frogs of the Hybridogenetic Rana esculenta Complex

Abstract

ABSTRACT.-CIOSeIy related clonal and sexual populations may coexist in spite of the theorized lower potential for the evolution of clonal genotypes. Water frogs of the Rana esculenta complex have hemiclonal inheritance b'ut most populations coexist with one of the recombinant parental species. We examine whether hemiclonal lineages may counterbalance their limitations of genetic variability by the adoption of one or more non-exclusive mechanisms: the general-purpose genotype or the frozen niche-variation model. Three coexisting hemiclones of the hybrid R. esculenta (GUll, GUT2, GLIT3) and both parental species (syntopic R. lessonae and allopatric 1?, ridibunda) were raised at two larval densities to examine morphological traits affecting jumping performance at the time of metamorphosis and size-independent jumping ability tested at three temperatures. Hind leg length and body mass at metamorphosis, traits that explain most of the variance in jumping performance, differed across hemiclones of R. esculenta. Metamorphs of hemiclone GUTI had the longest hindlimbs and were bigger than metamorphs of the other hemiclones at low larval density but not at high density. Size adjusted jumping performance exhibited a significant genotype by larval density interaction. Metamorphs of GUT1 showed maximal jumping performance when raised at low larval density but at high density metamorphs of GUT2 were the best jumpers. In addition, within particular traits, differences were found between hemiclones across densities. These results appear to be consistent with both frozen niche-variation model and the general-purpose genotype model. Comparison with parental species revealed syntopic it lessonae was smaller than hemiclones at metamorphosis but conversely exhibited better size-adjusted jumping performance when raised at low larval density. Temperature affected sizeadjusted jumping performance only for frogs raised at low larval density but not for those raised at high larval densities. There was no significant temperature by hemiclone interaction, Asexual reproduction is rare as a mode of genetic inheritance among vertebrates. Only approximately 80 unisexual taxa have been described, which represent 0.1% of known vertebrate species (White, 1978; Vrijenhoek et al., 1989). Theories that attempt to explain the widespread occurence of sexual reproduction are typically based on the assumption that asexual and sexual genotypes are fundamentally similar except for the sexual individuals' ability to produce genetically diverse progeny. It is also assumed that natural selection operates on these diverse genotypes enabling populations to evolve in response to changing environments. However, if this last assumption is discounted, asexual lineages should rapidly replace their sexual ancestors, because most escape the cost of producing males. This supplementary reproductive cost of producing males in sexuals determines the "paradox of sexuality" (Williams,

Developmental plasticity mirrors differences among taxa in spadefoot toads linking plasticity and diversity

“…In addition, there has been ample opportunity for selection to act on morphology. Relative limb length and head length have functional relevance for locomotion and feeding, and their plasticity in relation to shifts in life-history traits has been studied in detail (34,(49)(50)(51)(52). Observed plastic changes in morphology within species were relatively minor (1-5% in length), and they were unlikely to have a high impact on locomotor performance or predator escape efficiency (31), and thus they were unlikely to have large effects on fitness and to be the direct target of natural selection.…”

Effects of induced variation in anuran larval development on postmetamorphic energy reserves and locomotion

“…The consequences of size at metamorphosis for subsequent growth and survival can be mediated at least in part by locomotor performance and storage of energy reserves. Only a few studies have examined the effects of factors operating during the larval period on measures of performance of recently metamorphosed anurans (John-Alder and Morin 1990; Goater et al 1993;Semlitsch et al 1999;Tejedo et al 2000a;Tejedo et al 2000b) and to our knowledge none of these evaluated the effects of developmental temperature or larval diet on postmetamorphic performance. Although our results show, as others have before (e.g.…”

How important are skeletal muscle mechanics in setting limits on jumping performance?

“…Data on take-off velocity were taken from Toro et al (Toro et al, 2004); data on muscle masses were taken from Vanhooydonck et al (Vanhooydonck et al, 2006b). esculenta explained 77% of the variation in maximal jump distance, whereas body mass only explained 1% of the variation in performance (Tejedo et al, 2000).…”