The Evolutionarily Significant Unit (ESU) was conceptualized in 1986 as a conservation unit below the species level, theoretically applicable to a wide range of taxa. The concept has gained support, and various definitions or criteria, some of which are inconsistent with each other, have since been proposed. Recent critiques of the ESU have pointed out the dominance of definitions biased to the identification of long-term isolation or neutral genetic variation, which has largely ignored the adaptive components. We present here the validity of such claims and show how the ESU definitions have actually been applied in research. We surveyed scientific journals for original papers supporting ESU designations and determined who among the proponents of ESU definitions have gained wider support. Our results indicate that indeed there are inconsistencies with the original concept and with the existing definitions. Although the original concept recommended both ecological and genetic data as the basis for identification of ESUs, which reflect true evolutionary variation, recent definitions have become biased to either neutral genetic variation or adaptive variation. The definition which uses genetic data to assess neutral genetic variation (long-term isolation) has gained major support, and therefore validates the earlier claims. To bridge the gap between the original concept and the practical application, we propose the use of partial ESU and full ESU designations. The application of full ESU should be limited solely to when both information about neutral genetic variation and adaptive variation are available. In other cases, in which only a part of the variation is examined, we should use the term partial ESU (e.g., molecular-based ESU) and continue to investigate focal populations from other aspects of variations to designate full ESU.
We examined the vertical stratification of forest wildlife, from the ground up to the canopy layer, within a 2-hectare permanent plot of lowland evergreen rainforest on the Mt. Makiling Forest Reserve. Our aim was to determine the species richness of the different forest layers and evaluate their ecosystem services. Understorey, sub-canopy and canopy sampling were conducted during July 2016, March to April 2017 and February to March 2018, respectively. We were able to record a total of 68 species, consisting of 11 amphibians, 15 reptiles, 25 birds and 17 mammals. Increasing species richness with increasing vertical stratification was observed for both reptiles and mammals. For birds, the peak richness was observed in the sub-canopy and then decreased in the canopy. A decreasing trend was observed with amphibians wherein the peak species richness was observed in the understorey. Increasing vertical stratification influenced vertical habitat use and species richness. For the similarity index, the same pattern was observed for all species groups. Highest similarity was observed between the sub-canopy and the canopy and the least similarity was observed between the understorey and canopy. These results indicate that the understorey and the canopy host different species groups, thus, sampling of the understorey alone, often done in biodiversity surveys, may lead to the underestimation of species richness in an area.
Abstract. Alcazar SMT, Lit Jr IL, Rebancos CM, Barrion-Dupo ALA, De Guia APO, Bantayan NC, Alvarez JDV. 2020. Short communication: Diversity of cave-dwelling bats in Cebu Island, Philippines. Biodiversitas 21: 3249-3254. The species composition and richness of cave-dwelling bats in 16 caves of Cebu Island were studied to provide resource managers and local government units in Cebu baseline information that may be used toward conservation and sustainable utilization and management of local cave resources. Stationary and mobile mist-netting were employed at the entrance and dark zones of the caves to maximize the capture of bats. The study accounts for 15 species of cave bats, of which two were unidentified but are believed to be potentially new species, namely Rhinolophus sp. and Myotis sp., and three are new distribution records to Cebu, namely Rhinolophus philippinensis, Eonycteris robusta, and Megaderma spasma. In terms of richness values, Balay’g Agta holds six species and the remaining caves have less than five species. The presence of endemic, potentially new species and new distribution records of bats presents high conservation value and raises concern and calls for urgent action to protect the caves and the resources therein.
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