Increased potential for shell competition among hermit crabs (Pagurus beringanus and Pagurus granosimanus) in the rocky intertidal

We examined the prevalence and shell use of two species of hermit crabs (Pagurus granosimanus and Pagurus beringanus) in exposed and protected microhabitats at five sites in the rocky temperate intertidal on San Juan Island, Washington, to compare present habitat partitioning and potential interspecific competition to that reported nearly 50 years ago. We found that, in contrast to previous findings, the two species of hermit crabs overlapped extensively at some sites, typically those with less wave action. While the hermit crabs typically inhabited certain types of shells significantly more than others, and that use was congruent across microhabitats and species of hermit crabs at the same site, the dominant domicile differed substantially across sites. We provide a more complete ranking of shell use than previous authors and note site-specific dominant shell use. We conclude that previous habitat partitioning by depth may have weakened at protected sites. We hypothesize that increasing temperatures have caused P. granosimanus to expand its range deeper into the intertidal, which may increase the degree of interspecific competition for shells at the edge of the species’ tidal height range, where they overlap. Whether the habitat shift by this hermit crab is due to recent alterations in climate (particularly elevated temperatures, ocean acidification and lower local open ocean salinity) is unknown, but warrants further study.

Integrating voice and phenotype in a revision of the brush cuckoo Cacomantis variolosus (Aves: Cuculidae) complex

Brush cuckoos of the Cacomantis variolosus complex, which range from Southeast Asia to Australia and the Solomon Islands, have undergone much taxonomic upheaval. Here we examine 389 vocal recordings, 832 skins, and records of brood parasitism and habitat partitioning to shed light on their species and subspecies taxonomy. Bioacoustic analysis revealed seven distinct vocal groups. Among morphological markers, shape and proportions of the tail were found to be supporting indicators, in addition to plumage tone and pattern. Integration of the resulting data set distinguished six species-level taxa within the complex: sepulcralis in the Philippines and Sundaland east to central Nusa Tenggara, virescens in Sulawesi and the Sula Archipelago, aeruginosus in the Moluccas, variolosus in east Nusa Tenggara, the Moluccas, north and east Australia, New Guinea and Bismarck Archipelago, blandus in the Admiralty Islands, and addendus in the Solomon Islands. Our review of infra-specific differentiation among species leads us to distinguish 13 subspecies. All taxa identified are listed in a summary classification of the complex. Taxon diversity is greatest in the Moluccas, where two habitat-partitioned species and five allopatric subspecies occur, of which one species and three subspecies are endemic to this region.

Phylogeny and evolution of habitat preference in Goniurosaurus (Squamata: Eublepharidae) and their correlation with karst and granite-stream-adapted ecomorphologies in species groups from Vietnam

Maximum likelihood (ML) and Bayesian inference (BI) analyses using two mitochondrial (16S and cyt b) and two nuclear (CMOS and RAG1) genes and 103 specimens recovered the first phylogenies of all 23 extant species of Goniurosaurus. The analyses strongly supported the recognition of four monophyletic species groups with identical inter-specific relationships within the kuroiwae, lichtenfelderi, and yingdeensis groups but discordant topologies at some nodes within the luii group. Both analyses recovered a polyphyletic G. luii with respect to G. kadoorieorum, and owing to the lack of diagnostic characters in the latter, it is considered a junior synonym of G. luii. A stochastic character mapping analysis of karst versus non-karst habitat preference suggested that karstic landscapes may have played a major role in the evolution and diversification of Goniurosaurus. A karst habitat preference is marginally supported as the most probable ancestral condition for Goniurosaurus as well as for the kuroiwae, luii, and yingdeensis groups. However, a non-karst habitat preference is marginally supported as the most probable ancestral condition for the lichtenfelderi group. Multivariate and univariate ecomorphological analyses of the karst-adapted G. catbaensis, G. huuliensis, and G. luii of the luii group and the granite-stream-adapted G. lichtenfelderii of the lichtenfelderi group demonstrated that their markedly statistically different body shapes may be an adaptive response that contributes to habitat partitioning in areas of northern Vietnam where they are nearly sympatric.

Habitat Partitioning in the Marine Sector of Karst Subterranean Estuaries and Bermuda's Marine Caves: Benthic Foraminiferal Evidence

Karst subterranean estuaries (KSEs) are created from the two- and three-way mixing of saline groundwater, rain, and oceanic water in the subsurface on carbonate landscapes, and this hydrographic framework promotes unique physical processes, biogeochemical cycling, and biological communities. Here we provide evidence that the source and quantity of particulate organic matter (POM) that is delivered to the benthos strongly correlates to benthic habitat partitioning in the oxygenated marine sectors of KSEs. A dataset of benthic foraminifera at 128 different locations from several large flooded cave systems in Bermuda were compiled and evaluated against common environmental characteristics (e.g., tidal exposure, substrate particle size, bulk organic matter, C:N, total organic carbon, and δ13Corg). Benthic areas receiving more carbon isotopically depleted organic matter sources (mean δ13Corg values < −23.2‰, C:N ratios >11), most likely from the terrestrial surface and some marine plankton, were dominated by Trochammina inflata, Bolivina spp., and Helenina anderseni. In contrast, benthic areas receiving more carbon isotopically enriched organic matter sources (mean δ13Corg values > −21.6‰, C:N ratios <10), most likely from marine plankton transported through marine cave openings cave from adjacent coastal waters, were dominated by Spirophthalmidium emaciatum, Spirillina vivipara, Patellina corrugata, and Rotaliella arctica. The benthic foraminifera most distal from any cave entrances were dominated by taxa also known from the deep-sea (e.g., Rotaliella, Spirophthalmidium) in sediment with the lowest bulk organic matter content (mean: 6%), or taxa that prefer hard substrates and are potentially living attached to cave walls (Patellina, Spirillina). While physical groundwater characteristics (e.g., salinity, dissolved oxygen) are expected drivers of benthic ecosystems in KSEs, these results suggest that POM source, quantity, and delivery mechanisms (e.g., groundwater-seawater circulation mechanisms, terrestrial flux) play an important role in benthic habitat partitioning and the spatial variability of biogeochemical cycles in the oxygenated marine sector of KSEs.

Habitat use of co-occurring burying beetles (genus Nicrophorus) in southeastern Ontario, Canada

The coexistence of closely related species plays an important role in shaping local diversity. However, competition for shared resources can limit the ability of species to coexist. Many species avoid the costs of coexistence by diverging in habitat use, known as habitat partitioning. We examine patterns of habitat use in seven co-occurring species of burying beetles (genus Nicrophorus Fabricius, 1775), testing the hypothesis that Nicrophorus species partition resources by occupying distinct habitats. We surveyed Nicrophorus abundance and 54 habitat characteristics at 100 random sites spanning an environmentally diverse region of southeastern Ontario, Canada. We found that three species occupied distinct habitat types consistent with habitat partitioning. Specifically, Nicrophorus pustulatus Herschel, 1807, Nicrophorus hebes Kirby, 1837, and Nicrophorus marginatus Fabricius, 1801 appear to be specialists for forest canopy, wetlands, and open fields, respectively. In contrast, Nicrophorus orbicollis Say, 1825, Nicrophorus sayi Laporte, 1840, and Nicrophorus tomentosus Weber, 1801 appear to be generalists with wide breadths of habitat use. We were unable to identify the habitat associations of Nicrophorus defodiens Mannerheim, 1846. Our findings are consistent with habitat acting as an important resource axis along which some Nicrophorus species partition; however, divergence along other resource axes (e.g., temporal partitioning) also appears important for Nicrophorus coexistence.