Reproductive ecology of a Tibetan frogNanorana parkeri(Anura: Ranidae)

Abstract

Endemic to the Tibetan Plateau, Nanorana parkeri figures among the highest altitude amphibians in the world. The present work, which was conducted in an alpine marsh at 4300 m altitude, is the first report of the species' reproductive ecology. The breeding season, as indicated by the presence of amplectant pairs and fresh eggs in ponds, lasted from early Mary to early July. The ratios of adult male to female were 1.3 in hibernation ponds and 2.3 in spawning ones. Males were smaller than females. Amplexus was typically axillary (81.7%), with a few exceptional amplexus in which a male clasped another male or object rather than gravid females. Scramble competition occurred in 6.8% of the normal amplexus located. The body sizes of amplexed couples correlated positively. Deposited eggs were attached to submerged plants solitarily (60.5%) or in small clusters (39.5%), and the scattered arrangement of individual eggs could be a strategy to ensure embryonic development in oxygen-poor environments. Clutch size averaged 189 [standard deviation (SD) = 64], and correlated positively with female body size; egg size averaged 2.18 mm (SD = 0.10), independent of female body size; both traits within a clutch were negatively related with each other even controlling for female body size. Relatively few and large eggs laid by the Tibetan frogs, compared with those by lowland aquatic-spawning anuran species, should be adaptive to the harsh high-altitude conditions. Larvae hatched from eggs after 16.4 days on average (SD = 5.8). Froglets emerged between late July and early August, but some tadpoles were present in winter. These findings may help to understand the evolution of amphibians in extreme environments and to protect these remote species.

Assortative mating in space and time: patterns and biases

“…The distribution of body size can also vary throughout a breeding season. For example smaller pairs in amplexus of the Tibetan frog Nanorana parkeri are known to become more frequent as the season progresses (Lu et al 2016). Large individuals of the orb-web spider Trichonephila clavata also sexually mature early in the breeding season, whereas smaller individuals mature later (Miyashita 1994).…”

“…Note that such bias could even act within population, especially when the sampling scale exceeds the scale of choice (Rolán-Alvarez et al 2015). In addition, the magnitude of the traits used during mate assortment and their distribution likely naturally vary among populations and over time (Miyashita 1994;Lu et al 2016;Ng et al 2016). Consequently, pooling data can result in relatively higher measures for mate assortments because of mixing the average trait differences with assortment estimates and thereby increasing the apparent prevalence of positive assortative mating (see Rolán-Alvarez et al 2015).…”

“…In addition, the magnitude of the traits used during mate assortment and their distribution likely naturally vary among populations and over time (Miyashita 1994; Lu et al . 2016; Ng et al . 2016).…”

Aristotle, Buddhist scripture and embryology in ancient Mexico: building inclusion by re-thinking what counts as the history of developmental biology

“…Indeed, some Tibetan frog species produce embryos over 2 mm in diameter, making them readily observable, even without magnification (e.g. Chen et al, 2013 ; Lu et al, 2016 ). But, as entertaining as this line of thinking may be, scholarship demands us to acknowledge that just because those images look like frog embryos to a modern developmental biologist, it is not actually evidence of the artists’ intent.…”