Ecological Guild Evolution and the Discovery of the World's Smallest Vertebrate

Abstract

Living vertebrates vary drastically in body size, yet few taxa reach the extremely minute size of some frogs and teleost fish. Here we describe two new species of diminutive terrestrial frogs from the megadiverse hotspot island of New Guinea, one of which represents the smallest known vertebrate species, attaining an average body size of only 7.7 mm. Both new species are members of the recently described genus Paedophryne, the four species of which are all among the ten smallest known frog species, making Paedophryne the most diminutive genus of anurans. This discovery highlights intriguing ecological similarities among the numerous independent origins of diminutive anurans, suggesting that minute frogs are not mere oddities, but represent a previously unrecognized ecological guild.

Biological Scaling Problems and Solutions in Amphibians

“…Amphibians range in length over 250-fold. At one extreme is the smallest known vertebrate at 7 mm long, the frog Paedophryne amanuensis (Rittmeyer et al 2012), whereas the Goliath frog ( Conraua goliath ) can grow up to 33 cm, and the Chinese salamander ( Andrias davidianis ) to 1.8 m (Frost 2014). …”

Heterochrony: the Evolution of Development

“…The 29 smallest species (with the smallest having an average body length of just 7.7 millimeters) are spread across five families and 11 genera (Rittmeyer et al 2012). As well as very reduced size, these frogs have reduced fecundity and show paedomorphic traits of reduced ossification and lack of digits.…”

“…As well as very reduced size, these frogs have reduced fecundity and show paedomorphic traits of reduced ossification and lack of digits. Moreover, many of these frogs are direct developers, lacking a tadpole stage, and as such form a distinct ecological guild (Rittmeyer et al 2012).…”

The developmental hourglass model: a predictor of the basic body plan?

“…For example, despite the various niches inhabited (aquatic, terrestrial and aerial environments) and the over 1000-fold difference in body size [the smallest vertebrate is a frog less than 1 cm long (Rittmeyer et al, 2012) and the largest is the 30 m blue whale], all vertebrates share a set of anatomical features, such as a dorsally located central nervous system, segmented trunk muscles, vertebrae along the anteroposterior axis, a complex head with sensory organs (eyes, inner ear and nose), and organs such as the brain, heart and liver (Benton, 2004). Similarly, various other animal groups are also said to have a conserved basic body plan within their phyla.…”