Molecular analysis of Gigaspora (Glomales, Gigasporaceae)

This work presents a cooperative effort to integrate new molecular (isozyme and SSU analyses) characters into the morphological taxonomy of the genus Gigaspora (Glomales). Previous analyses of published Gigaspora SSU sequences indicated the presence of a few polymorphic nucleotides in the region delimited by primers NS71-SSU 1492'. In our study, the SSU of 24 isolates of arbuscular mycorrhizal (AM) fungi from the Gigasporaceae were amplified and the NS71-SSU 1492' region was directly sequenced. The corresponding sequences of four more isolates of AM fungi from Gigasporaceae, already published, were also included in our analyses. Three Gigaspora groups were identified on the basis of a 6 nucleotide-long 'molecular signature': Gigaspora rosea group ( G. rosea + G. albida ), Gigaspora margarita group ( G. margarita + G. decipiens ) and Gigaspora gigantea , which constituted a group by itself. The isozyme profiles (malate dehydrogenase, MDH) of 12 of these 28 isolates, and seven other isolates not sequenced, were compared. The results obtained further supported the grouping of isolates provided by the SSU analysis. Both SSU and MDH analysis indicated that two out of the 35 isolates had been misidentified, which was confirmed when their morphology was reassessed. The use of the Gigaspora intrageneric molecular signature as a quick, unambiguous and objective method to recognize Gigaspora isolates under any (field or laboratory) experimental conditions is suggested.     

A review of the bloodsucking midges of Trinidad and Tobago,West Indies (Diptera:Ceratopogonidae)*

Data are presented recording the presence of 49 species of bloodsucking cerato-pogonids in Trinidad, West Indies. Of these, 45 are Culicoides, one is a Leptoconops, and three belong to Forcipomyia (Lasiohelea). Five species are reported from Tobago: three Culicoides, one Leptoconops, and one Lasiohelea. The males of Culicoides benarrochi and C. fluviatilis are described for the first time, and the female of C. debilipalpis is redescribed. Culicoides filariferus and C. pseudodiabolicus are resurrected from synonymy, and characters are presented distinguishing them from C. diabolicus and C. guttatus. Biological data and keys to genera and species are included.     

The food and feeding ecology of Mugilidae in the St. Lucia lake system

The diet and feeding interrelationships of ten species of Mugilidae were studied over a two-year period in the St. Lucia lake system of South Africa. Qualitative stomach analyses were performed on over 1000 fish of more than 5 cm (standard length). All are soft bottom substrate feeders ingesting inorganic particles mixed with food items. The food of most species is the same and consists of Assiminea bifasciata , foraminifera, the large centric diatom Aptinoptychus splendens , small centric and pennate diatoms, and filamentous algae. Individual species of mullet however, differ, in the size of inorganic particles ingested and exhibit marked sand grain size preferences. The consumption of the various food items may depend upon their occurrence on substrates of the preferred particle size. There is no apparent change in diet and particle size preference according to age in any of the species and no seasonal variation was recorded in the diet. It is suggested that interspecific competition for food is reduced by substrate particle size selection and perhaps by differences in feeding periodicity. Where there is an apparent overlap in diet, as in the case of Assiminea bifasciata , on substrates of the same size then there is a superabundance of the food organism which serves to minimize competitive interactions.     

Landscape genetic structure of coastal tailed frogs (Ascaphus truei) in protected vs. managed forests

Habitat loss and fragmentation are the leading causes of species’ declines and extinctions. A key component of studying population response to habitat alteration is to understand how fragmentation affects population connectivity in disturbed landscapes. We used landscape genetic analyses to determine how habitat fragmentation due to timber harvest affects genetic population connectivity of the coastal tailed frog (Ascaphus truei), a forest-dwelling, stream-breeding amphibian. We compared rates of gene flow across old-growth (Olympic National Park) and logged landscapes (Olympic National Forest) and used spatial autoregression to estimate the effect of landscape variables on genetic structure. We detected higher overall genetic connectivity across the managed forest, although this was likely a historical signature of continuous forest before timber harvest began. Gene flow also occurred terrestrially, as connectivity was high across unconnected river basins. Autoregressive models demonstrated that closed forest and low solar radiation were correlated with increased gene flow. In addition, there was evidence for a temporal lag in the correlation of decreased gene flow with harvest, suggesting that the full genetic impact may not appear for several generations. Furthermore, we detected genetic evidence of population bottlenecks across the Olympic National Forest, including at sites that were within old-growth forest but surrounded by harvested patches. Collectively, this research suggests that absence of forest (whether due to natural or anthropogenic changes) is a key restrictor of genetic connectivity and that intact forested patches in the surrounding environment are necessary for continued gene flow and population connectivity.