Body size, competitive interactions, and the local distribution of Triturus newts

Abstract

Summary Pairs of EuropeanTriturus newt species of similar size tend not to co-occur syntopically, suggesting that similarity in body size is associated with competitive interactions that prevent coexistence. I tested this hypothesis with an experiment involving larvae of four species in 675-L artificial ponds. 2. There were strong interactions between most species pairs. Even the small T. helveticus had a clear impact on the larger T. alpestris . Pairs of species with different body sizes did not interact less strongly. 3. A standard increase in competitor biomass ( c. 2 g mass at metamorphosis) caused 42% lower expected survival from hatching to 1 year of age, regardless of whether the species were of similar or different size. In most cases this resulted from delayed metamorphosis, reduced size at emergence, and slightly lower larval survival. A standard increase in competitor density (0·74 individuals m− 2 ) caused a greater reduction in expected 1-year survival when the competitor was larger (18% decline) than when both species were of similar size (6% decline), primarily because the very large T. cristatus consumed the smallest species. 5. These findings suggest that species interactions during the larval stage cannot explain distribution patterns of same-and different-sized Triturus .

Influence of prey body characteristics and performance on predator selection

“…These traits have been widely linked to the probability of survival during a range of events, including predatory encounters (Litvak and Leggett 1992;Janzen 1993;Twombly and Tisch 2000;Dorner and Wagner 2003;Hoey and McCormick 2004;Alvarez and Nicieza 2006;Husak 2006) and competitive interactions (Smith 1990;Marshall et al 2006;Persson and De Roos 2006;Van Buskirk 2007;Zedrosser et al 2007), and threat of starvation and disease (Biro et al 2004;Lyons et al 2004;Bystrom et al 2006;Reim et al 2006;Hall et al 2007;Smith et al 2007). In recent years, the importance of these prey characteristics during predatory interactions has received considerable attention, as predation is widely thought to be one of the major processes influencing the size of populations and the structure of ecological communities (Sih 1987).…”

Costly neighbours: Heterospecific competitive interactions increase metabolic rates in dominant species

“…Larvae of both species frequently develop in the same water body 19 , and so freshly metamorphosed juveniles may interact in terrestrial shelters located near water 20, 21 . It could be expected that prolonged exposure to con- and heterospecific competitive interactions would induce plastic responses in SMR.…”

Kin discrimination during egg‐cannibalism in smooth newts: does competition matter?

“…Eggs, larvae and adults share the same habitats for several weeks, during which cannibalism of eggs and larvae by adult newts may take place (Bell & Lawton, 1975; Gabor, 1996). Kin recognition (avoidance of genetically similar mating partners; Jehle et al , 2007) and the negative effect of competition on larval fitness (in interspecific context at least; Van Buskirk, 2007) have also been demonstrated in this species. Although in a previous study, Gabor (1996) did not find any indication for that female smooth newts would discriminate their own eggs from non‐kin during cannibalistic foraging, this lack of kin discrimination may be due to the applied test conditions and does not exclude the possibility of kin discrimination under another set of circumstances (also see Gabor, 1996).…”