Relatedness and competitive asymmetry – the growth and development of common frog tadpoles

Abstract

Pakkasmaa, S. and Aikio, S. 2003. Relatedness and competitive asymmetry -the growth and development of common frog tadpoles. -Oikos 100: 55 -64.Individuals can compete either through direct interference or uptake of limiting resources. If competing individuals are able to recognize their relatives, relatedness of competitors may evoke kin selection, which favours relatively even resource share among relatives. Resource competition is often size-symmetric, i.e. proportional to an individual's biomass, while interference competition is asymmetric giving large individuals a disproportionate advantage over small individuals. Kin-selection is predicted to reduce the intensity of direct interference and competitive asymmetry, leading to increased mean and decreased variation in individual size. We tested these predictions by investigating the effects of relatedness on age and size at metamorphosis in the common frog Rana temporaria tadpoles in a laboratory experiment. We reared related (full-and half-sibs) and unrelated tadpoles of different sizes (small, large, small and large together) at two densities until metamorphosis. Relatedness had little effect on mean growth, but it reduced size variation, as measured with coefficient of variation. Furthermore, there was a significant interaction between relatedness and density in size at metamorphosis, so that relatives always grew better in lower density, but growth was less affected by density among unrelated individuals. This indicates that the effects of relatedness on tadpole performance may be context dependent. Initial size differences in the mixed size treatment evened out during the course of the experiment, and initially small tadpoles were able to compensate the early growth losses, although it took longer for them to reach metamorphosis. We conclude that although relatedness may have rather small effects on the growth and development of R. temporaria tadpoles, it increases the symmetry of resource share decreasing between-individual variation in size at metamorphosis.

The combined effects of food supply and larval density on survival, growth and metamorphosis of Chinese tiger frog (Hoplobatrachus rugulosa) tadpoles

“…Means with different superscripts differ significantly (Tukey's test, α = 0.05, a N b N c). earlier at a smaller body size than those in lower density (Browne et al, 2003;Hensley, 1993;Martinez et al, 1996;Pakkasmaa and Aikio, 2003;Stark et al, 2012); (2) food supply has a much more pronounced role than larval density in influencing the larval period; and (3) the extent to which development of tadpoles can be accelerated by reducing larval density is quite limited. In this study, the variance of metamorphosis time, which is a measure of developmental asynchrony, responded in a predictable way to the density and food treatments.…”

Effects of prochloraz and ethinylestradiol on sexual development in Rana temporaria

“…Species and race differences in developmental rate are probably the cause of this difference in sex ratio at metamorphosis. Moreover, animal density may play a role in the rate of development (Pakkasmaa and Aiko, 2003). Even though a small percentage of intersex in adults is natural (Witschi,'29a,b,'30), relatively high prevalence in adults, and in juveniles in species that normally exhibit direct development have Fig.…”

Larval fitness, microsatellite diversity and MHC class II diversity in common frog (Rana temporaria) populations

“…Growth rates of larval anurans can be a non-linear function of density, with an optimum above and below which growth is stunted (a so-called Allee effect, Wilbur, 1977). Intraspecific competition among anuran larvae, including R. temporaria, is well documented and can be affected by relatedness (Pakkasmaa and Aikio, 2003). It is also possible that deleterious alleles might be in the process of being purged from urban frog populations.…”