Hatching asynchrony, survival, and the fitness of alternative adult morphs in Ambystoma talpoideum

Abstract

The mole salamander, Ambystoma talpoideum, exhibits both aquatic (gilled) and terrestrial (metamorphosed) adult morphologies. Previous studies have shown the existence of body-size advantages associated with the terrestrial morph in A. talpoideum and other polymorphic salamanders (e.g., A. tigrinum). However, aquatic adult A. talpoideum mature at a younger age and often breed earlier than terrestrial adults. We tested the hypothesis that early maturation and reproduction in aquatic adults increase fitness (irrespective of body size). We reared larval A. talpoideum in mesocosms and varied the timing of hatching, with early-hatching larvae representing the offspring from early-breeding aquatic adults, and late-hatching larvae representing the offspring of later-breeding terrestrial adults. Our results demonstrate significantly higher survival rates among early-hatchlings relative to late-hatching conspecifics, supporting the hypothesis that early reproduction may be an important mechanism mediating the polymorphism in A. talpoideum. We discuss our results within the context of size-based models of the fitness of alternative life-cycles.

Density and intercohort priority effects on larval Salamandra salamandra in temporary pools

“…This result suggests a high level of cannibalism, due to greater size asymmetry between cohorts in individual treatment units (Collins and Holomuzki 1984;Reques and Tejedo 1996), and is consistent with other studies showing intercohort priority effects on survival in salamanders (Ryan and Plague 2004) and other cannibalistic species (Crowley et al 1987).…”

Life cycle polyphenism as a factor affecting ecological divergence within Notophthalmus viridescens

“…In polyphenic ambystomatid salamanders (A. talpoideum, A. tigrinum, and A. gracile), selection favors metamorphosis under drying aquatic conditions to escape deteriorating aquatic habitats. In contrast, paedomorphosis is selectively advantageous in permanent water because paedomorphs can have a greater reproductive potential by allowing more rapid growth, earlier maturation, and earlier breeding than metamorphic adults (Rose and Armentrout 1976;Semlitsch et al 1990;Whiteman 1994;Ryan and Semlitsch 1998;Ryan and Plague 2004). Therefore, the Wtness of alternative morphs can vary depending on pond hydroperiods.…”

Short-term variation in sperm competition causes sperm-mediated epigenetic effects on early offspring performance in the zebrafish

“…Nonetheless, the timing of hatching relative to competitor broods has been shown to have fitness effects in other externally fertilizing fish such as the Atlantic salmon Salmo salar; competition for larval feeding grounds may be strong and larvae arriving early at these feeding grounds appear to have an advantage compared with those arriving even a day later [53]. Also, positive fitness consequences for early offspring emergence have been demonstrated in a range of species, including mole salamanders Ambystoma talpoideum, where early hatching individuals were found to have higher survival rates than late hatching conspecifics [54]. Fitness advantages for early hatchers in asynchronously laying bird species are well documented (see for example [55], and references therein), as are the advantages for early hatching in lizards [56].…”