Can age and growth patterns explain the geographical variation in the body size of two toad species?

Abstract

Determining both the age structure and growth pattern allows to establish the causal factors, environmental and/or genetic, that eventually may be responsible for the observed pattern of divergence. We examined the variation in age structure and growth pattern across populations of two toad species, Pelobates cultripes and Epidalea calamita that exhibit a geographic variation in body size in southern Spain.For both species, populations differed in mean age but age structure did not correlate with body size variation across populations. Although the population with the youngest females found for E. calamita was the smallest in body size, the oldest males for both species were found in a small body size population. The growth pattern fi t well to a von Bertalanffy growth model and interdemic divergence were found for both the asymptotic body size (S m ) and the growth coeffi cients (k). As expected, Large-Bodied populations of both species attained higher S m but, Small-Bodied population had higher, although non signifi cantly different, k growth coeffi cients. Also, the Small-Bodied population attained sexual maturity sooner but had also high longevity. The observed pattern may refl ect both environmental variations in resources availability affecting body size observed across populations, but also different growth and maturity pathways that may respond to contrasting selective pressures.

El rol de la disponibilidad de alimento en la reducción del tamaño corporal asociada al sustrato arenoso en Pelobates cultripes

“…We also found considerable differences in larval development among populations of P. cultripes through common garden experiments, consistent with the geographic variation observed for adult body size . In addition, in our most recent study, comparing age structure and growth patterns across P. cultripes populations, we suggest both environmental variations in resources availability and divergent growth trajectories among populations (Marangoni et al, 2021). This steep variation also affects other amphibian species that inhabit the same studied area such as Epidalea calamita and newts, suggesting a strong environmental influence (Diaz-Paniagua et al, 1996;Díaz-Paniagua and Mateo, 1999;Hyeun-Ji et al, 2020 Refs;Marangoni et al 2021).…”

“…In addition, in our most recent study, comparing age structure and growth patterns across P. cultripes populations, we suggest both environmental variations in resources availability and divergent growth trajectories among populations (Marangoni et al, 2021). This steep variation also affects other amphibian species that inhabit the same studied area such as Epidalea calamita and newts, suggesting a strong environmental influence (Diaz-Paniagua et al, 1996;Díaz-Paniagua and Mateo, 1999;Hyeun-Ji et al, 2020 Refs;Marangoni et al 2021). In addition, reduced life-span was suggested as the main factor of body size reduction of Pelobates cultripes inhabiting sandy substrates of Sierra de Ariça (Portugal) (Leclair et al, 2005).…”

“…This is a continuous growth that becomes asymptotic after reaching sexual maturity, due to a trade-off in resource allocation occurs between reproduction and growth (Heino and Kaitala, 1999). This growth pattern will determine that interdemic variations in both juvenile growth rates to maturity and age of maturation, can promote divergences in adult size among populations (Marangoni et al, , 2021. Food availability is one of the most important factors determining juveniles and adult growth rate and consequently has strong effects on life-history traits such as survival and age at first reproduction (Arlettaz et al, 2017).…”

Modeling Sexual Differences of Body Size Variation in Ground Beetles in Geographical Gradients: A Case Study of Pterostichus melanarius (Illiger, 1798) (Coleoptera, Carabidae)

“…Clinal variation may indicate such local adaptation, as geographical clines are strongly related to environmental gradients, which may pose differential challenges to survival and reproduction. In addition, animals may also exhibit striking body size variation at smaller spatial scale for nearby locations with similar climate characteristics but with variation in microhabitat conditions, such as the nature of the substrate, which may impose nutritional and/or hydric constraints [63].…”

Sexual shape dimorphism in Bufo verrucosissimus (Pallas, 1814) from Lake Borçka Karagöl, Türkiye

“…In anurans, most species studied (~90%) are known to have a female-biased SSD (Shine 1979). Ultimately, this general trend is interpreted as a consequence of selection acting to increase female fecundity (Woolbright 1983, Monnet & Cherry 2002, Silva et al 2020), but, proximately, it can be attributed to intersexual differences in life-history traits such as growth rate, lifespan, or age at maturity (Han & Fu 2013;Alaei et al 2021, Marangoni et al 2021. Conversely, selective forces may favour larger body sizes in males by increasing reproductive success if larger males are preferred by females or if larger male have an advantage in male-male competition (Yu et al 2010, Hudson & Fu 2013.…”