Accurate morphological ant mimicry by Myrmarachne jumping spiders confers strong protective benefits against predators. However, it has been hypothesized that the slender and constricted ant-like appearance imposes costs on the hunting ability because their jumping power to capture prey is obtained from hydraulic pressure in their bodies. This hypothesis remains to be sufficiently investigated. We compared the jumping and prey-capture abilities of seven Myrmarachne species and non-myrmecomorphic salticids collected from tropical forests in Malaysian Borneo and northeastern Thailand. We found that the mimics had significantly reduced abilities compared with the non-mimics. The analysis using geometric morphometric techniques revealed that the reduced abilities were strongly associated with the morphological traits for ant mimicry and relatively lower abilities were found in Myrmarachne species with a more narrowed form. These results support the hypothesis that the jumping ability to capture prey is constrained by the morphological mimicry and provide a new insight into understanding the evolutionary costs of accurate mimicry.
A new species of the genus Castoponera Deeleman-Reinhold, 2001, Castoponera christae sp. n., is described here. The species is closely related to Castoponera lecythus Deeleman-Reinhold, 2001, but can be distinguished by the structures of the male palp and the female genitalia.
The genus Myrmarachne MacLeay, 1839 (Araneae: Salticidae) is one of the most diversified salticid groups in Southeast Asia, with 23 species previously recorded from Borneo. Based on the collections accumulated from 2004 to 2014 in the Lambir Hills National Park, we herein describe six new species: M. amabilis sp. nov., M. hashimotoi sp. nov., M. lagarosoma sp. nov., M. leptosoma sp. nov., M. salaputium sp. nov. and M. tintinnabulum sp. nov. In addition, we describe the female of M. endoi Yamasaki Ahmad, 2013 for the first time. The male-female combination in M. amabilis sp. nov., M. tintinnabulum sp. nov. and M. endoi were confirmed by DNA barcoding.
The genus Utivarachna Kishida, 1940 currently comprises 23 species, with eight described from Borneo. We examined the type materials of the Bornean species, except for U. fukasawana Kishida, 1940, as well as newly collected specimens. As a result, we describe a new species, Utivarachna itiokai sp. nov., which belongs to the dusun-group. We also provide the first description of the female of Utivarachna ichneumon and redescribe the known Utivarachna species of Borneo.
Most canopy species in lowland tropical rain forests in Southeast Asia, represented by Dipterocarpaceae, undergo mast reproduction synchronously at community level during a general flowering event. Such events occur at irregular intervals of 2-10 years. Some species do not necessarily participate in every synchronous mast reproduction, however. This may be due to a lack of carbohydrate resources in the trees for masting. We tested the hypothesis that interspecific differences in the time required to store assimilates in trees for seed production are due to the frequency of masting and/or seed size in each species. We examined the relationship between reproductive frequency and the carbon accumulation period necessary for seed production, and between the seed size and the period, using radiocarbon analysis in 18 dipterocarp canopy species. The mean carbon accumulation period was 0.84 years before seed maturation in all species studied. The carbon accumulation period did not have any significant correlation with reproductive frequency or seed size, both of which varied widely across the species studied. Our results show that for seed production, dipterocarp masting species do not use carbon assimilates stored for a period between the masting years, but instead use recent photosynthates produced primarily in a masting year, regardless of the masting interval or seed size of each species. These findings suggest that storage of carbohydrate resources is not a limiting factor in the masting of dipterocarps, and that accumulation and allocation of other resources is important as a precondition for participation in general flowering.
Pycnotarsobrentus inuiae Maruyama & Bartolozzi, gen. nov. and sp. nov. (Brentinae: Eremoxenini) is described from the Lambir Hills National Park, Borneo (Sarawak, Malaysia) based on specimens collected from Crematogaster difformis F. Smith, 1857 ant nests in the myrmecophytic epiphytic ferns Platycerium crustacea Copel. and Lecanopteris ridleyi H. Christ. A second species of Pycnotarsobrentus is known from Malaysia but is represented by only one female and consequently not yet described pending discovery of a male. Pycnotarsobrentus belongs to the tribe Eremoxenini and shares some character states with the African genus Pericordus Kolbe, 1883. No species of Eremoxenini with similar morphological modifications are known from the Oriental region.