Age structure of a lizard along an elevational gradient reveals nonlinear lifespan patterns with altitude

Abstract

Lifespan is one of the main components of life history. Shorter lifespans can be expected in marginal habitats. However, in the case of ectotherms, lifespan typically increases with altitude, even though temperature—one of the main factors to determine ectotherms’ life history—declines with elevation. This pattern can be explained by the fact that a shorter activity time favors survival. In this study, we analyzed how lifespan and other life-history traits of the lizard Psammodromus algirus vary along a 2,200 m elevational gradient in Sierra Nevada (SE Spain). Populations at intermediate altitudes (1,200–1,700 m), corresponding to the optimal habitat for this species, had the shortest lifespans, whereas populations inhabiting marginal habitats (at both low and at high altitudes) lived longest. Therefore, this lizard did not follow the typical pattern of ectotherms, as it also lived longer at the lower limit of its distribution, nor did it show a longer lifespan in areas with optimal habitats. These results might be explained by a complex combination of different gradients along the mountain, namely that activity time decreases with altitude whereas food availability increases. This could explain why lifespan was maximum at both high (limited activity time) and low (limited food availability) altitudes, resulting in similar lifespans in areas with contrasting environmental conditions. Our findings also indicated that reproductive investment and body condition increase with elevation, suggesting that alpine populations are locally adapted.

Age structure and growth pattern of a high‐altitude lizard population based on age determination by skeletochronology

“…The femurs, humeri, and phalanges have better consistency and resolution than the other bones. This result is also consistent with previous findings in other species (Castanet, 1994; Comas et al, 2020; Guarino et al, 2019; Lu et al, 2018; Santoyo‐Brito et al, 2018; Smirina & Ananjeva, 2007). Although age could be underestimated by LAGs in phalanges, it only occurs in a few very‐old individuals (Table 1).…”

“…This inference is confirmed by the results reported previously (Lu et al, 2018). However, this result differs from the pattern prevalent in reptiles wherein populations from higher altitudes generally have higher longevity (Comas et al, 2020;Sindaco et al, 2010;Wapstra & Swain, 2001). Furthermore, Lu et al (2018) also indicated that the high-elevation population has shorter longevity but a larger SVL, and the low-elevation population has longer longevity but a smaller SVL.…”

Fire reduces parasite load in a Mediterranean lizard

“…Psammodromus algirus is a medium-sized ground-dwelling lizard with a lifespan of 3-5 years [34]; it is widespread in Mediterranean landscapes of the Iberian Peninsula where high-intensity fires are common. Although it is a habitat-generalist species [35], it prefers habitats with low shrub cover [36].…”

“…To test if as a result of the cleaning effect of fire, lizards in postfire conditions suffer less cumulative parasitic infections than those living in unburned areas, and considering the life expectancy of P. algirus (approx. 3 years [34]), we sampled lizards at five locations in which the time since fire was 2-4 years (hereafter, 'older' wildfires). In such cases, we counted the number of raised ventral scales of the lizards in order to estimate the level of parasitism in lizards that have spent most of their lives under postfire conditions.…”

Phenological and intrinsic predictors of mite and haemacoccidian infection dynamics in a Mediterranean community of lizards

“…Acanthodactylus erythrurus is the biggest [up to 8 cm snout-vent length (SVL)] and most thermophilic species of the three (Belliure et al ., 1996 ; Verwaijen and Van Damme, 2007 ). Although little is known about the exact life span of the species in the wild, the results of several studies allow to order the species from shorter to longer expected life span (Carretero and Llórente, 1991 ; Drechsler and Monrós, 2019 ; Comas et al ., 2020 ). Following this statement, A. erythurus has an intermediate life span, which is not known in detail, but the results in Drechsler and Monrós ( 2019 ), with 80% yearly renewal indicate that it seems to be around two years for most individuals in this population.…”