Mitsuru Ohira

Nested subset patterns of species composition in a pond-dwelling fish fauna

Our objectives are to examine the influence of the difference in stress tolerance among species on patterns of nestedness and to test whether a set of several small ponds supports more species than a few large ponds of equal area. Although fish species assemblages for each group of all fish, tolerant and intolerant species were significantly nested, intolerant species showed stronger nested tendency than tolerant species, suggesting that the tolerance of species can influence the patterns of nestedness. These results suggest that the tolerance of species can influence the patterns of nestedness. As for the comparison of cumulative species richness in small ponds and large ponds, although small ponds supported more species for tolerant species, there was little difference for intolerant species.

Threatened fishes of the world: Lefua echigonia (Jordan and Richardson 1907) (Balitoridae)

Common name: Hotokedojo (in Japanese). Conservation state: EN in the Red Data Book of Japan (Ministry of the Environment of Japan 2003). Identification: D 7–9; P1 11–12; P2; 6–7; LR 90–122. Flattened head; mouth downward; incomplete lateral line; maximum length about 90 mm TL. A normally patchy pattern is found on the side of body (Masuda et al. 1984). The karyotype is 2n=50 (Suzuki and Taki 1982). Illustration by M. Chibuka. Distribution: Endemic to Japan. It is found from the south to north of Honshu and Shikoku (approximately 40°−33°N). Abundance: The surviving populations are extremely small and isolated. Habitat and ecology: It is usually found in small headwater streams in lowland areas. Adults stay in the slow current or static water (Mitsuo et al. 2007), and feed primarily on benthic or planktonic invertebrates. In addition, L. echigonia is thought to be a key host fish for glochidia of Unionidae (Toshishige and Maruyama 2005). The breeding season is from late March to early June. Individuals mature within 1 to 2 years, and females deposit adhesive eggs on litter or vegetation. Fecundity, on average, 1500 eggs (Suguro 2005). Threats: Habitat loss resulting from urbanization and river improvement. Most remaining habitats are severely fragmented. Conservation action: An artificial breeding technique has been established (Suguro 2002). Conservation recommendations: Several studies revealed genetic characteristic of L. echigonia (Saitoh et al. 2003; Saka et al. 2003; Mihara et al. 2005), and indicated that L. echigonia were divided into five or six distinct groups (Saka et al. 2003; Mihara et al. 2005). Conservation requires not only protection of remaining habitats at the local level but also planning and management at the regional level to keep genetic diversity. Environ Biol Fish (2009) 86:307–308 DOI 10.1007/s10641-009-9511-6