Research on longevity and associated age data of South American anurans: trends, gaps and recommendations

Abstract

Longevity is one of the most important characteristics in the life history of organisms. It is directly associated with growth, reproduction and age of sexual maturity. Despite this, little is known about longevity in South American anuran species, a region considered as a hotspot of world diversity. Thus, we carried out a literature review of publications on longevity of South American anurans that used the skeletochronology method to identify the main publication trends, as well as to point out the main information gaps and suggest future directions. We found clear biases when we analysed temporal, spatial and taxonomic patterns in publications on longevity: (i) studies are recent (mostly from 2015 onwards), (ii) bufonids and leptodactylids were the most studied groups, (iii) medium to large species are the most studied, (iv) species with wide geographic distribution, low risk of extinction, (v) the studies are concentrated in Brazil and Argentina, and (vi) most studies are in the Chaco biogeographical sub-region. We suggest that future work prioritizes little explored families and with high species diversity, small-bodied species, with restricted distribution, threatened with extinction, in order to expand the representation of different evolutionary lineages along the biogeographical units of South America.

Keywords: amphibia; demography; review; skeletochronology.

Figure 1.

(a) Number of articles on skeletochronology of South American anurans published by year. The brown line represents the cumulative number of articles. (b) Percentage of studies on the longevity of South American anurans published by country.

Figure 2.

Map of South America, highlighting countries (a) and biogeographical regions according to [42] (b) Yellow dots represent skeletochronology studies with anurans recovered in our survey.

Figure 3.

Ecological characteristics of the species, expressed as percentage. (a) habitat type, (b) species geographic distribution and (c) IUCN category.

Figure 4.

Number of anuran species per family and the number of South American species for which longevity is known (inside the silhouettes). Hy = Hylidae; Bu = Bufonidae; Le = Leptodactylidae; Mi = Microhylidae; Od = Odontophrynidae; Hlo = Hylodidae; Cy = Cycloramphidae; Ce = Ceratophryidae; Of = other South American anuran families. Gray and black hatched bar = sum of species without longevity data. The silhouettes are not to scale. Anuran families according to Vasconcelos et al. [37].

Figure 5.

(a) Ratio of the sample number of males and females per family used in the studies. (b) Average body size of anuran species used in skeletochronology studies per family, in South America. Average body size (SVL) data of the species were taken directly from the articles and the average of the SVL found for each family was calculated. Hy = Hylidae; Bu = Bufonidae; Le = Leptodactylidae; Mi = Microhylidae; Od = Odontophrynidae; Hlo = Hylodidae; Cy = Cycloramphidae; Ce = Ceratophryidae; Gray line = standard deviation; Gray and orange hatched bar = general average size of the species.

Figure 6.

Estimated longevity (in years) for each South American anuran family using skeletochronology. Green bars = male longevity; purple bars = female longevity; the values within the silhouettes represent the number of species in each family for which longevity work has been published. The silhouettes are out of scale.