Faunal Transition Zone Research Articles

Tapeworms in Rodents from the Lower Anabar River Basin, with a Review of Species Diversity of Cestodes in Yakutia, Russia.

We aimed to explore the first data on the fauna of cestodes in rodents from the Lower Anabar River Basin situated in extreme north-western Yakutia, Russia and to develop a biological and biogeographical framework for examination of the species diversity of cestodes from Yakutia, which is an important faunal transition zone in the eastern Palaearctic. Field inventory of cestodes from rodents was conducted for the first time in the region of north-western Yakutia. Species diversity, intensity and prevalence of infection were assessed. It was noted a rather high (up to 82.5%) total cestode prevalence in rodents in the extreme north-western area of Yakutia. In Arvicolinae hosts, we collected specimens of six cestode species of four genera and three families. Arostrilepis microtis and Douthittia nordenskioeldi were first collected in voles Lasiopodomys gregalis from Yakutia (new host and geographical records). The zoonotic parasite Echinococcus multilocularis was found in the liver of L. gregalis. The list of cestodes from rodents in Yakutia based on review of previous publications and the material obtained in the present study includes 24 species of 16 genera and five families. Out of these, 17 parasitise rodents as adults stage and seven as larvae. The fauna of rodent tapeworms from the south subarctic tundra and pre-tundra larch woodlands of the north-western Yakutia is characterised by relatively impoverished species diversity compared to the fauna of cestodes from the taiga zone of the central Yakutia. The decrease in the species diversity of tapeworms does not affect the total infection prevalence of the definitive hosts, which is relatively high in this region.

A new species of freshwater mussel in the genus Popenaias Frierson, 1927, from the Gulf coastal rivers of central Mexico (Bivalvia: Unionida: Unionidae)with comments on the genus.

The Gulf coastal drainages of central Mexico are a faunal transition zone between North and South America and harbor a unique assemblage of freshwater mussels (Bivalvia: Unionida). However, little information is available regarding the taxonomy, distribution, and evolutionary history of the Mexican mussel fauna due to limited sampling over the last 100 years. To address these knowledge gaps, we evaluated species-level diversity in the genus Popenaias Frierson, 1927, in Mexican Gulf coastal drainages as part of a larger effort to inform conservation efforts for members of this genus both in Mexico and the United States of America. Based on our analyses, we describe Popenaias berezai n. sp. from the Río Valles of the Río Pánuco basin, San Luis Potosí, Mexico. We also provide presumptive distributional range, phylogenetic structure, and molecular and morphological diagnoses of the new species and provide comments on the other species currently in Popenaias. Our findings highlight the high levels of endemism among freshwater mussels in Mexican Gulf coastal drainages and will help guide impending conservation actions for P. popeii, which is listed as "endangered" in the United States.

Phylogeography of the eight-barbel loach Lefua nikkonis (Cypriniformes: Nemacheilidae): how important were straits in northern Japan as biogeographical barriers?

Many straits in the Japanese archipelago have been proposed as biogeographical boundaries, but there is disagreement regarding their importance as historic barriers against dispersal of terrestrial and freshwater taxa. Mitochondrial DNA haplotype and phylogenetic analyses of Lefua nikkonis, a primary freshwater fish inhabiting northern Japan and descendent from Siberia, revealed that the species is genetically structured within its geographic range, but that two major haplotypes are widely distributed across the Ishikari Lowland of Hokkaido Island as well as across the Tsugaru Strait between Hokkaido and Honshu Islands, two well-known biogeographical boundaries of northern Japan. The two major haplotypes were separated from each other by only one mutational step, and many other haplotypes, including those endemic to the region south of these barriers, have diverged from the major haplotypes, suggesting rapid range expansion and local differentiation. Divergence-time estimates, based on vicariance of the Honshu endemic congener L. echigonia via uplift of the Central Highlands, demonstrated that the southward dispersal of L. nikkonis from Hokkaido Island to Honshu Island occurred less than 0.08–0.19 Mya, suggesting that a land bridge emerged at the Tsugaru Strait during the Riss glaciation. Given that other freshwater taxa crossed the strait earlier (during the Middle Pleistocene), it is likely that land bridges in the strait have repeatedly emerged. The fact that L. nikkonis invaded only the northern part of Honshu, and that many other freshwater species also have the limit of their distribution ranges in this area as well, indicates that a faunal transition zone might persist even without the Tsugaru Strait. Thus, straits and lowlands in northern Japan are likely to have been less important as dispersal barriers to freshwater taxa than is currently thought.

Phylogenetic tests of a Cercopithecus monkey hybrid reveal X-chromosomal polyphyly of C. cephus and emerging patterns in the cephus species group radiation

A captive Cercopithecus nictitans × C. cephus male was examined at loci on the X- and Y-chromosomes as a test of previously described phylogenetic methods for identifying hybrid Cercopithecus monkeys. The results confirm the reliability of such assays, indicating that they can be of immediate utility for studies of wild populations in Gabon, where the two species have hybridised. A closer examination of the resultant sex chromosomal topologies, combined with recent mitochondrial studies, reveals two emerging patterns in the evolution of the cephus species group. First, all three genetic systems (X-DNA, Y-DNA and mtDNA) agree that the earliest divergence separates West African from Central African species, consistent with a major faunal transition zone in the vicinity of the Cross River. Second, the X-DNA and mtDNA trees reveal polyphyly of C. cephus lineages. It is unclear at present whether these polyphylies are due to ancestral hybridisation or incomplete lineage sorting, or both.

Indochinese‐Sundaic faunal transition and phylogeographical divides north of the Isthmus of Kra in Southeast Asian Bulbuls (Aves: Pycnonotidae)

AbstractAimFor terrestrial organisms, a faunal transition zone between the Indochinese and Sundaic regions is delimited north of the Isthmus of Kra on the Thai‐Malay Peninsula. We used a mitochondrial marker to test the predicted location of intraspecific north–south divides for four species of bulbuls (Pycnonotus). Phylogenetic relationships among Thai‐Malay populations and their closest relatives from the Greater Sundas were reconstructed from a multilocus data set including 35 Pycnonotus species.LocationIndochina, Thai‐Malay Peninsula, Greater Sundas.MethodsWe sampled target species along a north–south transect spanning the Isthmus of Kra and reconstructed phylogeographical patterns based on ND2 haplotype networks. Phylogenies were reconstructed using Maximum likelihood and Bayesian inference. Divergence time estimates were inferred from single‐locus and multilocus data using *beast.ResultsWe found mitochondrial north–south divides in all target species. Haplotypes of southern genetic clusters were distributed all across the Thai‐Malay Peninsula and north into Central Thailand. Local overlap of genetic lineages was confirmed at one location in one species only. In three of the focal species, the southern limits of southern haplotype clusters were restricted to the Thai‐Malay Peninsula and did not extend into the Greater Sundas. Peninsular north–south divides were dated to the late Pleistocene, whereas Indochinese‐Sundaic lineage divergence was dated to the late Pliocene.Main conclusionsPopulation boundaries did not coincide with the Isthmus of Kra, but instead were located north of the Thai‐Malay Peninsula in Central Thailand. Only one of four divides represented an Indochinese‐Sundaic transition. Different phylogeographical patterns among target species were presumably shaped by different ecological preferences in Pleistocene palaeohabitats. Pliocene Indochinese‐Sundaic lineage divergence in bulbuls coincides with strong vegetational changes on the Peninsula that shaped two phytogeographical transitions. Distribution limits of bird species roughly coincide with these transition zones and therefore the avifaunal Thai‐Malay transition represents a broad zone rather than a sharp boundary.

Effect of environmental factors on the abundance of decapod crustaceans from soft bottoms off southeastern Brazil

This study investigated the importance of variations in environmental factors affecting the abundance patterns of decapods on the southeastern Brazilian coast. Sampling was carried out monthly from January 1998 through December 1999 in Ubatumirim and Mar Virado, Ubatuba region, using a commercial shrimp fishing boat equipped with double-rig nets. Six areas adjacent to rocky shores were chosen. Bottom-water samples were collected using a Nansen bottle, to measure the temperature and salinity. Sediment samples were also obtained by means of a Van Veen grab, for determination of texture and organic-matter content. The association of environmental factors with species abundance was evaluated by Canonical Correspondence Analysis (α = 0.05). Forty-one species of Decapoda were used in the multivariate analysis. The analysis indicated that sediment texture (phi) and bottom temperature were the main factors correlated (p < 0.05) with the spatial and temporal abundance of the species. Considering the study region as faunal transition zone, including a mixture of species of both tropical and subantarctic origin, the species responded differently to environmental factors, mainly temperature. It is conceivable that the decapods adjust their distribution according to their intrinsic physiological limitations, possibly as a result of the available resources.

Genealogical approaches to the temporal origins of the Central American gap: Speciation and divergence in Pacific &lt;i&gt;Chthamalus&lt;/i&gt; (Sessilia: Chthamalidae)

A large section of the tropical Eastern Pacific coastline is nearly devoid of reef or consolidated habitat, and is known as the Central American Gap as it is associated with a biogeographic transition in fish and invertebrate species. We analyze phylogeographic data for intertidal barnacles (Chthamalus) to identify relevant temporal patterns that describe the origins of this biogeographic transition (the Mexican-Panamic Transition Zone). These contrasts of populations on either side of the transition zone include two pairs of closely related species (C. panamensis and C. hedgecocki; C. southwardorum and a Southern form of C. southwardorum), as well as gene flow data within one species (C. panamensis) that currently is found on both sides of the boundary between provinces. Using sequence data from a prior phylogenetic study, we used traditional (net nucleotide divergence) measures as well as coalescent analyses that incorporate the isolation-migration model to identify the likely time of separation between Northern and Southern taxa in two species pairs. A total of 67 individuals were sequenced at two mitochondrial (cytochrome c oxidase I, 16S) and one nuclear (elongation factor 1-alpha) gene regions. Our analyses indicate that the regional isolation of these intertidal barnacles occurred approximately 315-400kya, with subsequent expansion of C. panamensis from the Southern region into the North much more recently. There are insufficient survey data to conclusively document the absence of species from this group within the Central American Gap region near the Gulf of Tehuantepec. However, appropriate habitat is quite sparse in this region and other environmental factors, including upwelling and water temperature, are likely to be associated with isolation of many species in the Mexican and Panamic provinces sensu stricto. Some taxa may maintain gene flow across this region, but very few genetic studies have been completed on such taxa. Until further work is done, distinguishing between prior hypotheses of a faunal gap, or a faunal transition zone, is somewhat speculative. Additional taxonomic revision will be necessary in Chthamalus but is beyond the scope of this paper.

Biogeographical Patterns of Marine Benthic Macroinvertebrates Along the Atlantic Coast of the Northeastern USA

The biogeography of marine benthic macroinvertebrates of US Atlantic estuaries and inshore coastal areas from Delaware Bay north to Passamaquoddy Bay was studied to compare recent data with historical biogeographic studies, define physical–chemical factors affecting species’ distributions, and provide information for calibrating benthic indices of environmental condition. Five years (2000–2004) of data from 614 non-polluted, soft-bottom stations from the National Coastal Assessment were analyzed. Multi-dimensional scaling done on Bray-Curtis similarity matrices of species’ relative abundance (547 species) suggested seven subregions: two based on salinity (oligohaline, mesohaline) and five based on latitude. Species’ distribution patterns for stations with salinities ≥18 (n = 558) were strongly influenced by latitude; Cape Cod was a clear faunal transition zone (R = 0.92, p < 0.001). Conversely, for stations with salinities <18 (n = 56), salinity was the more important factor. An ordination of abiotic variables (temperature, salinity, sediment percent silt-clay, depth) correlated well with the ordination of species’ relative abundance data (R = 0.77, p < 0.001). The first split of a multivariate regression tree was by a summer bottom temperature of 20°C at Cape Cod. Salinity and percent silt-clay led to further splits. These results support the existence of Virginian and Transhatteran biogeographic provinces. They constitute a baseline for addressing broad-scale and long-term issues such as global climate change, species invasions, and conservation planning.

ORIGINAL ARTICLE: Taxonomy and diversity of Afroalpine Chironomidae (Insecta: Diptera) on Mount Kenya and the Rwenzori Mountains, East Africa.

Aim Anthropogenic climate change is expected to result in the complete loss of glaciers from the high mountains of tropical Africa, with profound impacts on the hydrology and ecology of unique tropical cold‐water lakes located downstream from them. This study examines the biodiversity of Chironomidae (Insecta: Diptera) communities in these scarce Afroalpine lake systems, in order to determine their uniqueness in relation to lowland African lakes and alpine lakes in temperate regions, and to evaluate the potential of Afroalpine Chironomidae as biological indicators to monitor future changes in the ecological integrity of their habitat. Location Mount Kenya (Kenya) and Rwenzori Mountains (Uganda). Methods The species composition of Afroalpine chironomid communities was assessed using recent larval death assemblages extracted from the surface sediments of 11 high‐mountain lakes between 2900 and 4575 m. Results were compared with similar faunal data from 68 East African lakes at low and middle elevation (750–2760 m), and with literature records of Chironomidae species distribution in sub‐Saharan Africa, the Palaearctic region and elsewhere. All recovered taxa were fully described and illustrated. Results The 11‐lake analysis yielded 1744 subfossil chironomid larvae belonging to 16 distinct taxa of full‐grown larvae, and three taxa of less differentiated juveniles. Eleven of these 16 are not known to occur in African lakes at lower elevation, and eight taxa (or 50% of total species richness) appear restricted to the specific habitat of cold lakes above 3900 m, where night‐time freezing is frequent year‐round. The faunal transition zone coincides broadly with the Ericaceous zone of terrestrial vegetation (c. 3000–4000 m). Snowline depression during the Quaternary ice ages must have facilitated dispersion of cold‐stenothermous species among the high mountains of equatorial East Africa, but less so from or to the Palaearctic region via the Ethiopian highlands. Main conclusions Chironomid communities in glacier‐fed lakes on Africa's highest mountains are highly distinct from those of lowland African lakes, and potentially unique on a continental scale. By virtue of excellent preservation and their spatial and temporal integration of local community dynamics, chironomid larval death assemblages extracted from surface sediments are powerful biological indicators for monitoring the hydrological and ecological changes associated with the current retreat and loss of Africa's glaciers.

A krill-dominated micronekton and macrozooplankton community in Croker Passage, Antarctica with an estimate of fish predation

Abstract A micronektonic and macrozooplanktonic community was sampled with midwater trawls in the Croker Passage, vic. Antarctic Peninsula. Species composition suggested the area was a faunal transition zone between oceanic and nearshore communities. In a comparison between the study area and two oceanic areas, four of the top five numerically dominant species were identical ( Euphausia superba, Salpa thompsoni, Thysanoessa macrura and Sagitta gazellae ). In the nearshore region a mysid ( Antarctomysis ohlinii ) replaced the oceanic chaetognath Euhrohnia hamata in numerical ranking . E. superba was primarily responsible for the much higher nearshore biomass values when compared with those of oceanic regions (52.6 vs 2.4–3.1 g DM/m 2 ). The ctenophore Callianira antarctica , the mysid A. ohlinii , and the pelagic nototheniid fish Pleuragramma antarcticum were important neritic biomass species. Some oceanic species, notably S. thompsoni and the mesopelagic fish Electrona antarctica , were also important contributors to total micronektonic biomass. Fish predation by P. antarcticum and E. antarctica on E. superba (assuming constant fish and krill populations through the season that was sampled, the austral fall (90 d), and using our daily consumption values) is estimated at 2.5% and 2.9% of the total krill numbers, respectively, mostly on the juvenile segment of the population. Krill densities vary considerably in time and space, while available data suggest that pelagic fishes show less seasonal and spatial change. The most likely explanation for those observations is that the fishes are reliably more vulnerable to sampling gear than krill, but it also implies a consistent low level of fish predation on krill throughout the year, particularly on juveniles.

Delineating fish-habitat associations for spatially based management: an example from the south-eastern Australian continental shelf

A multi-scale, multi-gear survey identified the spatial structure and compositions of fish communities from a range of seabed types on the south-eastern Australian continental shelf (25 m to ~200 m depth). Most communities are species-rich and contain many shared species. Multivariate analysis of distributions of 201 fishes showed communities to be correlated with depth, latitude and seabed type;correlation with hydrodynamic climate is suggested by patterns in morphology. Depth-related patterns occurred on soft-sediment and hard substrata; strong latitudinal (south-west/north-east)patterns identify the area as a faunal transition zone with a major faunal disjunction extending across the shelf. Community patterns were overlaid on distributions of substrata to produce a biophysical map. This mapping process is discussed in the context of spatial management:the ecologically significant scale at which to map habitat features and definition of management units for ecosystem-based management. A hierarchy of scaled ecological units is being developed for Australia’s National Representative System of Marine Protected Areas (NRSMPA);given the scope of the NRSMPA initiative, surrogate measures of community structure will be required. Maps of substrata and topography, interpreted in the context of the broader depth and latitudinal community structure and as modified by hydrography, may provide one useful surrogate.

FISHERIES IN A SEA OF CHANGE: ECOLOGY AND OCEANOGRAPHY OF NEW ENGLAND'S FISHING GROUNDS

This paper serves to set the stage for the conference on the history, status, and future of New England's offshore fisheries. From a global perspective, it provides a brief overview of the geological, physical, and biological processes and features that make New England one of the world's most productive temperate shelf regions, exceeding the primary and secondary production of other renowned temperate fishing grounds. Bathymetry, climate, and tides create a complex mixing regime that enhances nutrient cycling and primary productivity especially over Georges Bank and northeast Gulf of Maine. The glacially influenced coast and seabed create a unique benthic habitat along the US east coast that is a nursery to lobsters and cod, two of the regions most valuable fisheries. Considering the diversity of its habitats, however, New England's marine fauna are rather impoverished due to extinctions related to polar cooling, glaciation, and the absence of suitable refuge habitat to the south. Today's faunal distributions are attributed to recovered ranges pushed south during the glaciation and reinvasions from Europe. The steep north-south thermal gradient along the coast makes it a faunal transition zone. Over the past four centuries, man has contributed to dramatic shifts in the composition of New England's marine biotic communities through harvesting and species introductions. Growing human pressure and the dynamic nature of the productivity of New England waters raise increasing concern over the sustainability of its fisheries.

Larval fish assemblages and water mass history in a major faunal transition zone

A region of distinct oceanographic features that result from the meeting of several water masses is marked by Cape Hatteras, North Carolina, between the Middle Atlantic Bight (MAB) and South Atlantic Bight (SAB). The features are dynamic, corresponding, in part, to the degree of water exchange between the MAB and SAB. The extent of larval fish transport via these features could have implications to fish population genetics, year-class structure, zoogeography, and access to nursery habitat. As a step in the examination of larval exchange between the MAB and SAB, we studied the association of spring larval fish assemblages with environmental variables descriptive of the water mass origins. The region was clearly an oceanographic and ichthyoplankton faunal transition zone. Larval distribution corresponded to patterns of adult distributions along the entire eastern seaboard. High taxa-environment correlations described a boundary assemblage strongly influenced by oceanographic conditions. Net assemblages from mixed waters were dominated by taxa with widespread adult distributions (e. g. Peprilus triacanthus, synodontidae, triglidae, clupiedae, others) rather than a mix of taxa from other groups. MAB water contained Limanda ferruginea and Benthosema glaciale in deep, cold water and Glyptocephalus cynoglossus, Hippoglossina oblonga, Scomber scombrus, Lophius americanus, and others in shallow, warmer, less saline water. High densities of numerous sub-tropical species, (e.g. Xyrichtys novacula, Bothus spp.) and low densities of many others were found in SAB waters but varied greatly in distribution with depth. Taxa varied in their fidelity to environmental indicators, thereby allowing for insight into the nature of the apparent differential permeability of this boundary zone to various species and into the precision of future predictions regarding transport related recruitment success.

The long-horned beetles of south Florida (Cerambycidae: Coleoptera): biogeography and relationships with the Bahama Islands and Cuba

South Florida is a floral and faunal transition zone between the Nearctic region and the West Indian part of the Neotropical region. Ninety-one species of Cerambycidae are known from the south Florida mainland and 53 species of Cerambycidae from the Florida Keys. The cerambycid fauna of south Florida is about equally of Neotropical (53%) and Nearctic origin (47%). Since the Florida Keys were entirely submerged several times in the Pliocene and Pleistocene epochs, the present cerambycid fauna is predominantly the result of late Pleistocene – Holocene overland dispersal from south-central Florida and overwater dispersal from the West Indies (Bahama Islands and Cuba). Species–area and species–distance relationships for the islands form significant regression lines as predicted by the equilibrium theory of island biogeography. 'The presence of a "distance effect" is surprising, since it is usually considered that only during the past 10 000 years has the southern tip of the Florida peninsula been fragmented into the present-day islands of the Keys by a rising sea level. An alternative geological scenario, supported by this study, suggests that the present islands of the Keys have appeared as the sea level fell only within the past 6000 years, and the fauna is a more recently derived one.

Distribution of dimorphic males of three species of Nematoscelis (Euphausiacea)

Samples collected from the eastern Atlantic Ocean between 40° and 4° N with rectangular and ring nets contained male specimens of Nematoscelis atlantica, N. microps, and N. tenella (Euphausiacea) with saddle-shaped thickenings of chitin on the dorsal surface of some abdominal segments, and with enlarged photophores on the abdominal segments immediately posterior to those with thickenings. Two forms of each species are distinguished by the number and the position of chitinous thickenings and enlarged photophores. Except in a zone off W. Africa (approximately between 22° and 16° N) each form of N. atlantica and N. microps occurs as a distinct population. These populations appear to be characteristic of either the North or South Atlantic Central water, and the overlap zone corresponds approximately with the physical boundary between these water masses and with a faunal transition zone found in this region by other workers. For N. tenella it appears that only one form occurs as a separate population south of 18° N in South Atlantic Central water. Between 28° and 18° N the two forms co-exist.