Multivariate characterisation of the habitats of seven species of Malayan mudskippers (Gobiidae: Oxudercinae)

Abstract

Mudskippers (Gobiidae: Oxudercinae) are amphibious gobies. The occurrence and habitats of seven sympatric species of Malayan mudskippers were recorded: Boleophthalmus boddarti, Boleophthalmus pectinirostris, Periophthalmodon schlosseri, Periophthalmus chrysospilos, Periophthalmus gracilis, Periophthalmus variabilis and Scartelaos histophorus. A total of 14 surveys were made at six localities along 120 km of the west coast of the Malay Peninsula in August 1996 and September 2006. A multivariate set of ordinal parameters were used to measure the quantity of environmental water in mudskippers' habitats, and three guilds of species were discriminated. The resulting pattern mirrored the adaptive scenario depicted by physiological and anatomical studies of mudskippers' terrestriality, although in one case a terminal taxon was less terrestrial than other more basal ones. Differentiation of trophic niches may also play a role in habitat selection by the herbivorous Boleophthalmus spp., which were only found in unvegetated, illuminated areas and on wet mud at low tide. With the more terrestrial guild, a significant negative co-occurrence suggested direct interspecific competition

Size variation of six species of oxudercine gobies along the intertidal zone in a Malayan coastal swamp

“…2), with decreasing densities of vegetation coverage from land to sea (Polgar & Crosa 2009). Stratum A included the higher forest, dominated by Rhizophora and Bruguiera spp.…”

“…Therefore, a visual census was made, always utilising 4 × 4 quadrats as sampling units. Specimens larger than about 5 cm TL were identified and counted in the field (Polgar & Crosa 2009) by binoculars (Sakura © , 10 × 42). Smaller individuals were then counted by approaching the quadrat at 1 to 2 m; the PVC pipes (width = 2.5 cm) delimitating the quadrat were used as a visual comparison for length estimates.…”

“…Several descriptive accounts (Milward 1974, Nursall 1981, Swennen et al 1995) and a few exploratory or semi-quantitative studies (Muhammad Ali & Norma-Rashid 2005, Polgar & Crosa 2009) reported a differential distribution of sympatric species along the intertidal gradient.…”

“…Therefore, this group offers the unique opportunity to make a comparative study of the evolution of semi-terrestriality. In particular, Murdy's morphological cladistic analysis (1989) suggests a sequential cladogenesis of increasingly terrestrial genera; nonetheless, the intrageneric variability in habitat selection according to indirect measures of the quantity of water present in the habitat during low tide (quantity of environmental water; Polgar & Crosa 2009) suggests that the adaptation to semiterrestrial habitats in oxudercine gobies may have been more complex than previously outlined.…”

“…Six oxudercine gobies from a Malayan intertidal ecosystem (Tanjung Piai, near the tip of mainland Asia; Fig. 1 The aims of this study were (1) to conduct the first community analysis of oxudercine gobies based on a random stratified sampling design; (2) to measure the spatial variation of oxudercine species along the intertidal zone in terms of relative abundance and size during low tide; (3) to explore possible associations between the observed spatial variation and several continuous and ordinal environmental parameters describing the availability of environmental water (Polgar & Crosa 2009); (4) to investigate whether synecological interactions can partly explain the distributional and co-occurrence patterns observed, at the spatial scale considered; and (5) to compare spatial distribution and species size patterns with the present phylogeny consensus at the genus level.…”