Age estimation through skeletochronology and mark-recapture of free-living Liolaemus leopardinus (Squamata: Liolaemidae) from Chile

Abstract

Age estimation through skeletochronology and mark-recapture of free-living Liolaemus leopardinus (Squamata: Liolaemidae) from Chile. Age determination is a crucial component of ecological studies. Researchers have relied on different methods and techniques, for example mark-recapture, body size, and skeletochronology, to assess the age of free-ranging individuals. We used all three methods to estimate the age structure of a population of Liolaemus leopardinus, a highly social and saxicolous lizard species endemic to the temperate region of central Chile. This high-elevation and secretive species is considered threatened and, although efforts have been made to reveal more specific details about the species' natural history, crucial details of its biology are still unknown. Our goal was to associate the number of Lines of Arrested Growth (LAGs) to snout-vent length (SVL) and use LAGs as an age estimation proxy on free-ranging individuals. For the skeletochronology analyses, a combination of toe-clips was collected when each subject was first captured in 2012-2013. SVL for all captured individuals was recorded during two different field seasons (austral spring to fall of 2011-2012 and 2012-2013). SVL data were also available for 10 individuals initially collected and permanently marked in 2005 (one juvenile and nine adults) and recaptured in 2011-2012. Three of those 10 subjects were captured again in 2012-2013. Our results revealed the formation of LAGs in L. leopardinus and a high degree of bone remodeling in both juveniles and adults. This bone remodeling combined with the high rapprochement in peripheral LAGs on the samples of the oldest lizards suggest that phalangeal bones are not suitable for age determination in this species. On the other hand, our mark-recapture results allowed us to assign individuals to four different age-classes when a subject's SVL was associated with activity periods and recaptures. Individuals of L. leopardinus are long-lived and their lifespan can exceed a decade. Female lizards become sexually mature at three to four years of age.Keywords: bone, body-length, high-altitude, lifespan, lines of arrested growth, lizards. 102Phyllomedusa -17(1), June 2018 Resumo Estimativa etária por meio de esqueletocronologia e marcação-e-recaptura de Liolaemus leopardinus (Squamata: Liolaemidae) do Chile. A determinação etária é um componente crucial de estudos ecológicos. Pesquisadores tem usado diferentes técnicas e métodos como marcação-erecaptura, tamanho do corpo e esqueletocronologia, para avaliar a idade de indivíduos na natureza. Usamos esses três métodos para estimar a estrutura etária de uma população de Liolaemus leopardinus, uma espécie de lagarto saxícola, altamente social e endêmica da região temperada do centro do Chile. Essa espécie secretiva de grandes altitudes é considerada ameaçada, e apesar dos esforços para descobrir detalhes específicos sobre a sua história natural, detalhes cruciais de sua biologia permanecem desconhecidos. Nosso objetivo foi associar o número de Linha...

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).…”

Viviparity imparts a macroevolutionary signature of ecological opportunity in Liolaemus lizards

“…The ability to maintain their field body temperature within their preferred range maximizes the locomotor performance of rock-dwelling individuals (L. sarmientoi) and likely determines their higher populational densities (compared with L. magellanicus) 74,75 . We hypothesize that once viviparous species colonize cold habitats by capitalizing on rocks to thermoregulate population densities then increase (a product of reduced predation and interspecific competition 76 ) driving high interspecific competition 77 , and this in turn promotes partitioning of rocky habitats and fast body size diversification. Sympatric species of Liolaemus usually differ in body size and the kind of rocks where they perch or retreat 78,79 .…”

“…Therefore, it is possible that viviparous Liolaemus from cold habitats have higher survival rates than their oviparous relatives from warm habitats, driving larger sizes. Likewise, as viviparous Liolaemus grow larger and reduce their predation risk 77 , they have larger heads, which in turn allows them to ingest a greater variety of food items 103 . As the high-elevation Andes are cradles of plant and insect diversity [104][105][106] , it is possible that viviparous species can consume more food than oviparous species, explaining their attainment of larger sizes.…”