At the lower size limit for tetrapods, two new species of the miniaturized frog genus Paedophryne (Anura, Microhylidae)

Abstract

I describe two new species in the miniaturized microhylid frog genus Paedophryne from forests in southeastern Papua New Guinea. The first species is described on the basis of two specimens and exhibits female snout-vent length of 8.5–9.0 mm (no males known), whereas that of the second species, described on the basis of 12 specimens, is 8.8–9.3 mm, with males 8.1–8.9 mm. These frogs are smaller than the other two diminutive species described when the genus was recently erected, and they represent what are currently the smallest known species of tetrapods. The two species replace each other elevationally on the same mountain massif and occur in relative geographic proximity to the other named species of the genus. Females of both species contain only two enlarged ova, suggesting that they also possess clutch sizes at the extreme lower end of variation in frogs. All species of Paedophryne inhabit leaf litter, as seen for most other miniaturized anurans.

Mountain colonisation, miniaturisation and ecological evolution in a radiation of direct-developing New Guinea Frogs (Choerophryne, Microhylidae)

“…A number of anuran lineages that approach the minimum size limits for vertebrates have been recently described (Wollenberg et al, 2008; Kraus, 2010a; Rittmeyer et al, 2012; Lehr & Coloma, 2008; Kraus, 2011; Wollenberg et al, 2008; Rittmeyer et al, 2012), and it has been suggested that miniaturised frogs may represent an often overlooked, but important ecological guild in tropical areas (Rittmeyer et al, 2012). Broadly, three patterns are globally apparent in miniaturised frogs: most lack a free-swimming tadpole stage (Estrada & Hedges, 1996); occur in wet tropical and usually insular regions; and are more-or-less terrestrial (Kraus, 2010a; Rittmeyer et al, 2012).…”

Morphological novelty and modest developmental truncation in Barboides, Africa's smallest vertebrates (Teleostei: Cyprinidae)

“…Miniaturization, the evolution of tiny adult body size, is widespread amongst animal taxa and is commonly associated with novel ecological, physiological, and morphological attributes (Hanken & Wake, ). Although perhaps most commonly encountered in groups of marine invertebrates (Hanken & Wake, ; Rundell & Leander, ), species with extremly small adult body size are known from all of the major groups of vertebrates, with many examples from amphibians and fishes (e.g., Britz, Conway, & Rüber, ; Das & Haas, ; Hanken & Wake, ; Kottelat, Britz, Tan, & Witte, ; Kraus, ; Parra‐Olea et al, ; Rittmeyer, Allison, Gründler, Thompson, & Austin, ). The phenotypes of miniaturized taxa are of interest because they represent unique combinations of reductions and structural simplifications often with novel traits that are not developed in their larger relatives (Britz & Conway, ; Hanken & Wake, ).…”

Male‐male competition and repeated evolution of terrestrial breeding in Atlantic Coastal Forest frogs*

“…For example, the increased risk of desiccation could select for larger body sizes for water conservation (Nevo ; Gouveia and Correia ; Gouveia et al. ) or locomotion and exploitation of leaf‐litter habitats could select for smaller body sizes (Lehr and Coloma ; Lehr and Catenazzi ; Kraus , ). These selective pressures should be similar for males and females, thus we predict that if these mechanisms are at work, size will vary equally in both sexes.…”

“…We used comparative analyses to test hypotheses about the evolutionary forces behind this reproductive diversification, and explored the potential selective drivers for the evolution of terrestriality. Specifically, we tested three hypotheses: (1) terrestriality evolved only once in this clade, as indicated by an earlier morphological phylogeny (Verdade ); (2) both males and females vary in overall sizes according to reproductive habitats (Nevo ; Lehr and Coloma ; Lehr and Catenazzi ; Kraus ; Kraus ; Gouveia and Correia ; Gouveia et al. ); and (3) males, but not females, decrease in size in terrestrial species because shifts to terrestriality impose lower sexual selection for large body sizes due to lower levels of male‐male competition (Zamudio et al.…”