Benthic Guilds Research Articles

Diatom metacommunity structuring in a large lake: geomorphic, water chemistry and dispersal effects on diatom guilds in Lake Ladoga (north-western Russia)

The relative importance of environmental filtering and dispersal in structuring metacommunities of littoral periphytic diatoms was assessed within a large lake (Lake Ladoga, north-western Russia). We hypothesized that different diatom functional guilds (high-profile, low-profile, motile and planktic) would respond differently to environmental and spatial variables, depending on their mode of attachment and dispersal ability. Guilds showed distinct distributional patterns along a gradient of wave-induced disturbance: low-profile diatoms dominated in exposed shorelines (high disturbance), whereas high-profile and motile diatoms were more abundant in coastal wetlands (low disturbance). Redundancy analysis with variation partitioning of the entire diatom community revealed that environmental variables (littoral geomorphology and water chemistry) outperformed spatial variables, indicating a predominant role of species sorting. When the diatom community was deconstructed into functional groups, benthic guilds (i.e., low-profile, high-profile and motile) showed higher dependence on environmental factors, whereas the planktic guild was primarily predicted by spatial factors. Thus, benthic taxa with lower dispersal abilities were less impacted by mass effects than planktic taxa. Among benthic guilds, motile diatoms were less sensitive to water chemistry compared to low-profile and high-profile diatoms, suggesting that a group-specific habitat preference may interfere with diatom responses to water quality changes. Hence, the response of diatom guilds to water quality parameters was related to their resistance to wave action. Overall, we concluded that the higher importance of environmental filtering than dispersal-related processes in shaping the diatom metacommunity resulted from a combination of a strong environmental gradient in geomorphology/water chemistry and the intermediate spatial scale of our study.

Fragmentation and dewatering transform Great Plains stream fish communities

Biodiversity in stream networks is threatened globally by interactions between habitat fragmentation and altered hydrologic regimes. In the Great Plains of North America, stream networks are fragmented by >19 000 anthropogenic barriers, and flow regimes are altered by surface water retention and groundwater extraction. We documented the distribution of anthropogenic barriers and dry stream segments in five basins covering the central Great Plains to assess effects of broad‐scale environmental change on stream fish community structure and distribution of reproductive guilds. We used an information‐theoretic approach to rank competing models in which fragmentation, discharge magnitude, and percentage of time streams had zero flow (a measure of desiccation) were included to predict effects of environmental alterations on the distribution of fishes belonging to different reproductive guilds. Fragmentation caused by anthropogenic barriers was most common in the eastern Great Plains, but stream desiccation became more common to the west, where rivers are underlain by the depleted (i.e., extraction > recharge) High Plains Aquifer. Longitudinal gradients in fragmentation and desiccation contributed to spatial shifts in community structure from taxonomically and functionally diverse communities dominated by pelagic reproductive guilds where fragmentation and desiccation were least, to homogenized communities dominated by benthic guilds where fragmentation and desiccation were common. Modeling results revealed these shifts were primarily associated with decline of pelagic reproductive guilds, notably small‐bodied pelagophilic and lithopelagophilic fishes that declined in association with decreased fragment length and increased number of days with zero flow. Graph theory combined with a barrier prioritization approach revealed specific fragments that could be reconnected to allow fishes within these guilds to colonize currently unoccupied fragments with the mitigation or removal of small dams (<10 m height). These findings are useful for natural resource managers charged with halting or reversing the prevailing pattern of declining fish diversity in the Great Plains. Our study represents one of the most comprehensive assessments of fish diversity responses to broad‐scale environmental change in the Great Plains and provides a conservation strategy for addressing the simultaneous contributions of fragmentation and flow alteration to the global freshwater biodiversity crisis.

Natural History ofParatelmatobius gaigeae(Amphibia, Anura, Leptodactylidae): Description of the Tadpole and Advertisement Call

The genus Paratelmatobius includes species that are usually rare and with limited distribution. As a result, data on natural history and larval morphology are still relatively scarce for some species. Here, we describe the tadpole of Paratelmatobius gaigeae and provide data on the reproductive biology and vocalization of the species. Both ecological and morphological features of the tadpole of P. gaigeae are similar to other tadpoles of the genus. The tadpole of P. gaigeae belongs to the exotrophic and benthic guild, with an anteroventral mouth, dorsally located eyes, identical dental formulae to the other species of the genus, and a large gap without papillae on the rostral portion of the anterior labium. The advertisement call is very short, pulsed, and consisting of single notes.O gênero Paratelmatobius inclui espécies usualmente raras e com distribuição limitada. Assim, dados sobre história natural e morfologia larval são ainda escassos para algumas de suas espécies. No presente trabalho nós descrevemos o girino de Paratelmatobius gaigeae e fornecemos dados sobre a biologia reprodutiva e a vocalização da espécie. A ecologia e a morfologia do girino de P. gaigeae são similares aos outros girinos do gênero. O girino de P. gaigeae pertence à guilda exotrófica e bêntica, com boca anteroventral, olhos posicionados dorsalmente, a mesma fórmula dentária das outras espécies do gênero e com um grande intervalo sem papilas na porção rostral do lábio anterior. O canto de anúncio é muito curto, pulsado e composto por notas isoladas.

Microhabitat use in an Assemblage of Native and Introduced Fishes in a Hawaiian Stream

Abstract: Ecological aspects of the relatively diverse fish assemblages found in the terminal reaches of streams in Hawai'i are largely unknown. This study described patterns of microhabitat use in an assemblage of native and introduced stream fishes living in the terminal reach of Wailoa Stream on the island of Hawai'i. Multivariate analyses of data collected through underwater visual surveys indicated that differences in microhabitat use were an important factor in structure of this assemblage. In riffle habitats, native fishes selected distinct microhabitats based on water velocity, substrate size, and position in the water column. In run habitats, a benthic guild (native gobies) and a water-column guild (introduced poeciliids and the endemic Kuhlia xenura) were identified. Strong differences in three-dimensional microhabitat use patterns appear to allow native gobioids to resist being displaced by introduced poeciliids in Wailoa Stream. However, high overlap in the microhabitat use patterns of juvenil...

Assessing the potential impact of an invasive species on a Mediterranean amphibian assemblage: a morphological and ecological approach

The introduction of exotic species is a major cause of ecological disturbance and has recently been shown to promote the decline of some amphibian populations. In Western Europe, several amphibian species have been introduced in recent decades, among them Discoglossus pictus, impact of which in native amphibian communities is still unknown. We studied the potential impact of D. pictus by analysing the degree of niche overlap, assuming the possible existence of competitive interactions with native species. We have studied the structure of the anuran assemblage at local level, defining the morphospace occupied by native species and the habitat occupied by the different ecomorphs. The analysis of distance matrices suggested that there was a covariation between morphological characters and habitat selection. We determined the position of D. pictus within the morphospace of the native anuran community, patterns of co-occurrence among alien, and native species and habitat selection. The potential effect of climate on local assemblages had been controlled based on data obtained from climate models. These analysis showed that D. pictus was clustered with the benthic guild, selected positively small ephemeral ponds and was a thermophilic species. Based on these results, a greater degree of niche overlap was expected with Bufo calamita and Pelodytes punctatus. The definition of morphological groups can be useful to understand the invaded assemblage structure and the potential effect of an alien frog on native communities.

Description of the tadpole of Telmatobius brevirostris (Anura: Ceratophryidae)

In Peru most tadpoles of the aquatic frogs genus Telmatobius belong to the lentic or lotic benthic guild. Members of this guild have a labial tooth row formula (LTRF) of 2/3, dorsolateral eyes, relative depressed bodies, dorsal fin do not extend beyond tail-body junction and they inhabit non flowing systems or microhabitats of non flowing portions of lotic systems (Altig & Johnson 1989, Aguilar et al. 2007, Aguilar & Lehr 2009). Only one species, T. atahualpai Wiens, is known to have a lotic rheophilous larva because it has a large oral disc, LTRF of more than 2/3, complete marginal papillae, numerous submarginal papillae and it inhabits streams (Altig & Johnson 1989, Aguilar & Lehr 2009). However, of the 25 Telmatobius species present in the Peruvian Andes (Frost 2010), tadpoles of only 11 species (44%) have been described, including the recently described tadpole of Telmatobius mayoloi Salas and Sinsch (Aguilar & Lehr 2009). Telmatobius brevirostris Vellard is endemic to central Peru, Huánuco region, with an altitudinal distribution ranging from 2000 to 3600 m.a.s.l. (Lehr 2005). Data on adult morphology, tadpole habitat, oral cavity and chondrocranium were given by Lehr (2005) and Aguilar & Valencia (2009), but tadpoles were left undescribed. Herein we describe the tadpole of T. brevirostris.

Long‐Term Trends in Habitat Use of Offshore Demersal Fishes in Western Lake Huron Suggest Large‐Scale Ecosystem Change

AbstractWe estimated mean depths of capture for offshore demersal fish species, grouped into three habitat‐based guilds (shallow benthic, pelagic, and deep benthic), using fall bottom trawl data (27–73 m) in the western main basin of Lake Huron from 1976 to 2007. The mean depth of capture of the shallow and deep benthic guilds initially exhibited a trend toward capture in shallower water, switched to a trend toward capture in deeper water in 1991, and changed back to a trend toward capture in shallower water in 2001–2002. Species in the pelagic guild showed a similar pattern, but the initial change point occurred in 1981 for this guild. Individual species in these guilds showed variable patterns of depth distribution, but a feature common to all guilds and all pelagic and deep benthic species was a change to a trend toward capturing fish in shallower water that occurred nearly simultaneously (1999–2002). These common trends suggest that large‐scale factors are affecting the habitat use of offshore demersal fish species in Lake Huron. The depth distributions of the three guilds have converged in recent years, indicating that the locations of suitable habitat for offshore demersal fishes may be changing. Our results indicate that the benthic ecology of the western main basin of Lake Huron is undergoing profound changes across a large spatial scale that are affecting the habitat use of offshore demersal fishes. We suggest that these changes are related to recent invasions of exotic species.

Monitoring with benthic macroinvertebrates: advantages and disadvantages of body size descriptors

1. The search for simple and effective descriptors of biological ecosystem components is a major challenge of monitoring aquatic ecosystem health. 2. The relevance of body-size-related descriptors of benthic invertebrate guilds in monitoring the health of transitional aquatic ecosystems is discussed. The rationale is that macroinvertebrate body size relates body-size–abundance distributions to disturbance pressures through individual energetics, population dynamics, interspecific interactions and species coexistence responses. 3. Body size is generally easy to measure and amenable to intercalibration procedures, it is comparable across taxa, guilds and sites, and, as a community feature, it is expected to vary on disturbance gradients, according to energetic and ecological constraints. 4. The mechanistic relevance of individual body size as a community feature, through coexistence relationships, still requires field and laboratory tests; standard methods to analyse body-size–abundance distributions are not yet fully developed. 5. Field experiments on coastal lagoons and freshwater ecosystems of southern Italy, which were designed to test the relevance of body-size-related constraints on the organization of detritus-based benthic guilds, are reviewed. 6. Study cases emphasized a number of interesting features of body size and related descriptors, that support their relevance as benthic invertebrates descriptors of ecosystem health: (a) body-size–abundance distributions are consistently less variable than taxonomic composition; (b) the width of body-size–abundance distribution is mainly due to the interspecific component; (c) the descriptors of body-size–abundance distributions seem to respond on environmental gradients and generally co-vary with species density, richness and diversity, on which most of the monitoring programmes actually rely. Copyright © 2004 John Wiley & Sons, Ltd.

Morphology of the prometamorphic larva of the spadefoot toad, Scaphiopus intermontanus (Anura: Pelobatidae), with an emphasis on the lateral line system and mouthparts.

We provide a detailed description of the larval morphology of the Great Basin spadefoot toad (Scaphiopus intermontanus), a species with documented morphological variability in larval structures associated with feeding. We based our findings on laboratory-raised individuals fed a herbivorous diet. We characterized the morphology of the prometamorphic larva (limited to developmental stages 37 and 38) and then related our findings to the larval ecology of the species. Based on its morphology, such as slightly depressed body, dorsally positioned eyes, anteroventrally oriented oral disc, intermediate tail fin height and slightly attenuated tail tip, relative lack of ventral neuromasts (compared to Xenopus laevis), and pigmentation banding patterns, and habits, such as selection of breeding sites by adults and larval foraging behavior, S. intermontanus can be characterized best as belonging to a (lentic-) benthic guild of anuran larvae. Nevertheless, the larvae are capable of occupying a broader array of ecological niches. Because we characterized individuals raised on a herbivorous diet, our morphological descriptions apply only to the herbivorous S. intermontanus larva (and perhaps to those larvae that are dietary generalists and may feed carnivorously only infrequently). Our findings can serve as a baseline for future morphological and developmental comparisons with the carnivorous morphological variant of this species.