The structure of carrion fly communities: the size and the type of carrion

Species composition and abundance relations of flies attracted to and bred from different sizes (20-100 g) and types of carrion (small mammal, cow liver, bird, and fish) were studied experimentally in natural breeding conditions in South Finland. Large pieces of carrion did not attract significantly more individuals or species than did small ones, but there was a positive correlation between size of carrion and numbers of flies bred, apparently because of competition. Altogether 10 species emerged from 50 cultures, and on average 2.78 ± 1.22 (SD) species emerged from one culture. The number of co-occurrences among the emerging flies indicated random colonization. Variation in species composition between like pieces of carrion was not less than variation between carcasses of different size or type; hence, size and type of carrion are not important determinants of community structure within the size and type ranges used.
Lucilia illustris (Meig.) was the predominant species, comprising 50% of flies trapped and 85% of flies bred. The difference indicates changing species composition in the community. Two sets of cultures were left open for egg-laying for 2 and 7 d. Competition was less Intensive in the former cultures, which produced 4.0 individuals per gram of carrion, contrasting with only 1.4 individuals per gram in the latter cultures. Competition delayed development in all species, but least in L. illustris , which suggests that fast developing species are at a competitive advantage. In agreement with this, abundance was positively correlated with the rate of development.     

Area effect of distribution of Silphids (Coleoptera,Silphidae) on Korean islands

We investigated the spatial patterns in the distribution of carrion beetles on 26 islands to test the area and distance effects on species diversity. The relationships between species richness and assemblage and island area, distance from the mainland, and shortest distance from the largest island within 2?km were analyzed using linear regression, Canonical Correspondence Analysis (CCA) and Multi-Response Permutation Procedures (MRPP). We hypothesized that both area and distance from the mainland played a significant role in species richness, while geographic location in the sea influenced aggregation of carrion beetles on islands. Area was the only factor influencing species richness of carrion beetles on islands. Moreover, distance from the mainland and close islands did not significantly influence to carrion beetles. In addition, geographic location in the same Sea did not influence beetle assemblages. Taken together, the results of this study indicated that carrion beetles on Korean islands were largely affected by island size and that dispersal was stochastic.     

How island size and isolation affect bee and wasp ensembles on small tropical islands: a case study from Kepulauan Seribu,Indonesia

Aim To study the effects of isolation and size of small tropical islands on species assemblages of bees (superfamily Apoidea) and wasps (superfamily Vespoidea). Location Twenty islands in the Kepulauan Seribu Archipelago off the coast of west Java, Indonesia. The size of surveyed islands ranges between 0.75 and 41.32 ha; their distance from the coast of Java varies between 3 and 62 km. Methods Field work was conducted from February to May 2005. Bees and wasps were caught with a sweep net during sampling units of 15 min, continuing until four consecutive samples revealed no new species. Total species richness was quantified by the estimators Chao 2, first‐order jackknife and Michaelis–Menten. The software binmatnest was used to test for nestedness of species assemblages. Similarities of species composition between islands were quantified by Sørensen’s similarity index. Results Eighty‐two species were recorded on the 20 surveyed islands. Species richness declined with increasing isolation of islands from the source area, Java. Although the size of the largest island exceeded that of the smallest island by a factor of almost 60, island size only very weakly affected species richness of bees; no effect of island size was found for wasps. Mean body size of species decreased with increasing island isolation. Nestedness of island faunas was only weakly developed. Species composition of both superfamilies was affected by island isolation, but not by island size. Main conclusions While the species–isolation relationship on the very small islands of Kepulauan Seribu followed the prediction of MacArthur and Wilson’s equilibrium theory, the absence of a species–area relationship indicated a weak ‘small‐island effect’, at least in wasps. The combination of an only weakly developed pattern of nested species subsets, the shift in species compositions and the decline of mean body size with increasing island isolation from the source area indicates that biotic interactions and different species traits contribute to the shaping of communities of bees and wasps within the archipelago. The potential of biotic interactions for generating distribution patterns of species within the archipelago is also emphasized by the observed restriction of some species with apparently high dispersal abilities to outer islands.     

Carrion mimicry in a South African orchid: flowers attract a narrow subset of the fly assemblage on animal carcasses

BACKGROUND AND AIMS: Although pollination of plants that attract flies by resembling their carrion brood and food sites has been reported in several angiosperm families, there has been very little work done on the level of specificity in carrion mimicry systems and the importance of plant cues in mediating such specialization. Specificity may be expected, as carrion-frequenting flies often exploit different niches, which has been interpreted as avoidance of interspecific competition. Interactions between the orchid Satyrium pumilum and a local assemblage of carrion flies were investigated, and the functional significance of floral traits, especially scent, tested. Pollination success and the incidence of pollinator-mediated self-pollination were measured and these were compared with values for orchids with sexual- and food-deceptive pollination systems. METHODS AND KEY RESULTS: Observations of insect visitation to animal carcasses and to flowers showed that the local assemblage of carrion flies was dominated by blow flies (Calliphoridae), house flies (Muscidae) and flesh flies (Sarcophagidae), but flowers of the orchid were pollinated exclusively by flesh flies, with a strong bias towards females that sometimes deposited live larvae on flowers. A trend towards similar partitioning of fly taxa was found in an experiment that tested the effect of large versus small carrion quantities on fly attraction. GC-MS analysis showed that floral scent is dominated by oligosulfides, 2-heptanone, p-cresol and indole, compounds that also dominate carrion scent. Flesh flies did not distinguish between floral and carrion scent in a choice experiment using olfactory cues only, which also showed that scent alone is responsible for fly attraction. Pollination success was relatively high (31·5 % of flowers), but tracking of stained pollinia also revealed that a relatively high percentage (46 %) of pollen deposited on stigmas originates from the same plant. CONCLUSIONS: Satyrium pumilum selectively attracts flesh flies, probably because its relatively weak scent resembles that of the small carrion on which these flies predominate. In this way, the plants exploit a specific subset of the insect assemblage associated with carrion. Pollination rates and levels of self-pollination were high compared with those in other deceptive orchids and it is therefore unlikely that this mimicry system evolved to promote outcrossing.     

Carrion fly‐derived DNA metabarcoding is an effective tool for mammal surveys: Evidence from a known tropical mammal community

Metabarcoding of vertebrate DNA derived from carrion flies has been proposed as a promising tool for biodiversity monitoring. To evaluate its efficacy, we conducted metabarcoding surveys of carrion flies on Barro Colorado Island (BCI), Panama, which has a well‐known mammal community, and compared our results against diurnal transect counts and camera trapping. We collected 1,084 flies in 29 sampling days, conducted metabarcoding with mammal‐specific (16S) and vertebrate‐specific (12S) primers, and sequenced amplicons on Illumina MiSeq. For taxonomic assignment, we compared blast with the new program protax , and we found that protax improved species identifications. We detected 20 mammal, four bird, and one lizard species from carrion fly metabarcoding, all but one of which are known from BCI. Fly metabarcoding detected more mammal species than concurrent transect counts (29 sampling days, 13 species) and concurrent camera trapping (84 sampling days, 17 species), and detected 67% of the number of mammal species documented by 8 years of transect counts and camera trapping combined, although fly metabarcoding missed several abundant species. This study demonstrates that carrion fly metabarcoding is a powerful tool for mammal biodiversity surveys and has the potential to detect a broader range of species than more commonly used methods.     

Dung beetle assemblages in forests and pastures of El Salvador: a functional comparison

This study examines the functional attributes of Neotropical dung beetles, and, based on the analysis, evaluates the role of dung beetles in pastures and tropical dry forest in El Salvador. Dung beetle diversity was lower in pastures than in forests. However, the total biomass of beetles at similarly-sized dung baits was frequently higher in pastures. Diversity loss followed structured patterns: (1) carrion and fruit feeding beetles were well represented (species number) in the forests but were largely absent from pastures; (2) large ball rollers and small fast tunnellers were present in forests but were absent from pastures; (3) large fast tunnellers and small slow tunnellers were poorly represented in pastures compared to forests but the few species that survived in pastures attained extremely high populations; and (4) each functional group in the species-poor pasture assemblages was divided almost equally into day and night active species. Substrate and habitat generalists that were present in both the forests and pastures were attracted to fruit and carrion in forested habitat but not in open pastures. In open habitats, flies and other insects may be the principal decomposers of decaying fruit and carrion.     

Factors influencing vascular plant diversity on 22 islands off the coast of eastern North America

Aim The influence of physiographic and historical factors on species richness of native and non‐native vascular plants on 22 coastal islands was examined. Location Islands off the coast of north‐eastern USA and south‐eastern Canada between 41° and 45° N latitude were studied. Island size ranges from 3 to 26,668 ha. All islands were deglaciated between 15,000 and 11,000 yr bp ; all but the four New Brunswick islands were attached to the mainland until rising sea level isolated them between 14,000 and 3800 yr bp . Methods Island species richness was determined from floras compiled or revised since 1969. Simple and multiple regression and rank correlation analysis were employed to assess the relative influence of independent variables on species richness. Potential predictors included island area, latitude, elevation, distance from the mainland, distance from the nearest larger island, number of soil types, years since isolation, years since deglaciation, and human population density. Results Native vascular plant species richness for the 22 islands in this study is influenced most strongly by island area, latitude, and distance from the nearest larger island; richness increases with island area, but decreases with latitude and distance from the nearest larger island as hypothesized. That a similar model employing distance from the mainland does not meet the critical value of P confirms the importance of the stepping‐stone effect. Habitat diversity as measured by number of soil types is also an important predictor of native plant species richness, but at least half of its influence can be attributed to island area, with which it is correlated. Two historical factors, years since deglaciation and years since isolation, also appear to be highly correlated with native species richness, but their influence cannot be separated from that of latitude for the present sample size. Non‐native vascular plant species richness is influenced primarily by island area and present‐day human population density, although human population density may be a surrogate for the cumulative effect of several centuries of anthropogenic impacts related to agriculture, hunting, fishing, whaling, tourism, and residential development. Very high densities of ground‐nesting pelagic birds may account for the high percentage of non‐native species on several small northern islands. Main conclusions Many of the principles of island biogeography that have been applied to oceanic islands apply equally to the 22 islands in this study. Native vascular plant species richness for these islands is strongly influenced by physiographic factors. Influence of two historical factors, years since deglaciation and years since isolation, cannot be assessed with the present sample size. Non‐native vascular plant species richness is influenced by island area as well as by human population density; human population density may be a surrogate for other anthropogenic impacts.     

Targeted detection of mammalian species using carrion fly‐derived DNA

DNA analysis from carrion flies (iDNA analysis) has recently been promoted as a powerful tool for cost‐ and time‐efficient monitoring of wildlife. While originally applied to identify any mammalian species present in an area, it should also allow for targeted detection of species and individuals. Using carrion flies captured in the Taï National Park, Côte d'Ivoire, we assessed this possibility by (i) screening carrion fly DNA extracts with nonspecific and species‐specific PCR systems, respectively, targeting mitochondrial DNA (mtDNA) fragments of any mammal or of Jentink's duiker (Cephalophus jentinki), three colobine monkeys (subfamily Colobinae) and sooty mangabey (Cercocebus atys); and (ii) genotyping carrion fly extracts containing sooty mangabey mtDNA. In comparison with the nonspecific PCR assay, the use of specific PCRs increased the frequency of detection of target species up to threefold. Detection rates partially reflected relative abundances of target species in the area. Amplification of seven microsatellite loci from carrion flies positive for sooty mangabey mtDNA yielded an average PCR success of 46%, showing that the identification of individuals is, to some extent, possible. Regression analysis of microsatellite PCR success and mtDNA concentration revealed that, among all carrion flies analysed for this study, 1% contained amounts of mammal mtDNA sufficient to attempt genotyping with potentially high success. We conclude that carrion fly‐derived DNA analysis represents a promising tool for targeted monitoring of mammals in their natural habitat.     

More species, fewer specialists: 100 years of changes in community composition in an island biogeographical study

Aim  We measured the changes in an island avifauna over more than 100 years (1898–2006), using community indices accounting for difference in expected species sensitivity to land-use and climate changes.
Location  Ouessant Island, France, Great Britain.
Methods  We assessed the temporal trend of the relative proportion of generalist species breeding on Ouessant island and whether high-temperature tolerant species have replaced less tolerant species over this time period. We further tested the relationship between the observed change in the avifauna composition, and long-term population species' trends measured independently in potential source regions of colonist species (France and Great Britain).
Results  During the whole study period, Ouessant island has experienced a strong increase in species richness (+41%), but a severe decline in specialist species. In contrast, we found no change in species composition in terms of their temperature-tolerance. The observed trend was highly correlated with species trends measured in the Great Britain.
Main conclusions  Our results revealed an ongoing biotic homogenization process towards more generalist species, coupled with a strong local increase in species richness. The observed trend was most likely driven by a strong habitat change in the island occurring during the period considered, favouring the colonization of generalist species. Our results show that an increase in species richness can be misinterpreted as a sign of conservation improvement and that assessing change in community composition using species-specific ecological traits provides more accurate insights for conservation planning purposes.     

Small island biogeography in the Gulf of California: lizards, the subsidized island biogeography hypothesis, and the small island effect

Aim We used insular lizard communities to test the predictions of two hypotheses that attempt to explain patterns of species richness on small islands. We first address the subsidized island biogeography (SIB) hypothesis, which predicts that spatial subsidies may cause insular species richness to deviate from species–area predictions, especially on small islands. Next, we examine the small island effect (SIE), which suggests small islands may not fit the traditional log‐linear species–area curve. Location Islands with arthropodivorous lizard communities throughout the Gulf of California. Methods To evaluate the SIB hypothesis, we first identified subsidized and unsubsidized islands based on surrogate measures of allochthonous productivity (i.e. island size and bird presence). Subsequently, we created species–area curves from previously published lizard species richness and island area data. We used the residuals and slopes from these analyses to compare species richness on subsidized and unsubsidized islands. To test for an SIE, we used breakpoint regression to model the relationship between lizard species richness and island area. We compared results from this model to results from the log‐linear regression model. Results Subsidized islands had a lower slope than unsubsidized islands, and the difference between these groups was significant when small islands were defined as < 1 km². In addition to comparing slopes, we tested for differences in the magnitude of the residuals (from the species–area regression of all islands) for subsidized vs. unsubsidized islands. We found no significant patterns in the residual values for small vs. large islands, or between islands with and without seabirds. The SIE was found to be a slightly better predictor of lizard species richness than the traditional log‐linear model. Main conclusions Predictions of the SIB hypothesis were partially supported by the data. The absence of a significant SIE may be a result of spatial subsidies as explained by the SIB hypothesis and data presented here. We conclude by suggesting potential scenarios to test for interactions between these two small island hypotheses. Future studies considering factors affecting species richness should examine the possible role of spatial subsidies, an SIE, or a synergistic effect of the two in data sets with small islands.     

Distribution and abundance patterns of bird community and raptor populations in the Andaman archipelago

A qualitative survey of the terrestrial bird community (sixty-five species) and a quantitative analysis of the five-diurnal raptor assemblage were earned out on 33 islands of the oceanic Andaman archipelago in the Bay of Bengal Among seven geographical parameters, island area was the main determinant of species richness for both the whole bird community and each category of species associated with four habitat types Species richness decreased most markedly with island size in the smallest islands and in open habitat species The rarest forest species were the most extinction prone with decreasing island size Specific habitat selection was the most prominent ecological correlate of inter island species distribution Observed species distribution patterns did not fit the random species placement or equprobable occurrence hypotheses Raptors were primarily forest species, two of them restricted to forest interior, two more tolerant of fragmentation and one naturally associated with mangroves Unexpectedly, the two rarest and most area sensitive raptors were the two smallest species with a strong active flight, whereas the most abundant and widespread species was the most forest interior and endemic taxon Both raptor species richness, species frequency of occurrence and abundance indices decreased with island area, which was consistently the most significant determinant of every species' occurrence and abundance There was a significant correlation between abundance or frequency of occurrence of every raptor species and the proportion of their preferred habitat type No relationship was found between habitat niche breadth or local abundance of any species and their distribution range among islands The hypothesis of random composition of species assemblages on islands was not supported because of species specific habitat selection Any evidence of interspecific competitive exclusion was limited to the striking habitat segregation of the two congeneric serpent eagles A metapopulation structure was suggested by small population distribution patterns, observed sea crossing and the circumstances of an apparent extinction     

Plants on small islands revisited: the effects of spatial scale and habitat quality on the species–area relationship

Understanding how species diversity is related to sampling area and spatial scale is central to ecology and biogeography. Small islands and small sampling units support fewer species than larger ones. However, the factors influencing species richness may not be consistent across scales. Richness at local scales is primarily affected by small‐scale environmental factors, stochasticity and the richness at the island scale. Richness at whole‐island scale, however, is usually strongly related to island area, isolation and habitat diversity. Despite these contrasting drivers at local and island scales, island species–area relationships (SARs) are often constructed based on richness sampled at the local scale. Whether local scale samples adequately predict richness at the island scale and how local scale samples influence the island SAR remains poorly understood. We investigated the effects of different sampling scales on the SAR of trees on 60 small islands in the Raja Ampat archipelago (Indonesia) using standardised transects and a hierarchically nested sampling design. We compared species richness at different grain sizes ranging from single (sub)transects to whole islands and tested whether the shape of the SAR changed with sampling scale. We then determined the importance of island area, isolation, shape and habitat quality at each scale on species richness. We found strong support for scale dependency of the SAR. The SAR changed from exponential shape at local sampling scales to sigmoidal shape at the island scale indicating variation of species richness independent of area for small islands and hence the presence of a small‐island effect. Island area was the most important variable explaining species richness at all scales, but habitat quality was also important at local scales. We conclude that the SAR and drivers of species richness are influenced by sampling scale, and that the sampling design for assessing the island SARs therefore requires careful consideration.     

Trophic associations of a dung beetle assemblage (Scarabaeidae: Scarabaeinae) in a woodland savanna of Botswana

Species richness and abundance of dung beetles were assessed across a range of bait types that acted as surrogates for the food resources available in Chobe National Park, Botswana. These bait types were comprised of the dung of pig (omnivore), cattle (ruminant herbivore dropping fine-fiberd pads), sheep (pellet-dropping ruminant herbivore), and elephant (monogastric, nonruminant herbivore producing coarse-fibered droppings), and chicken livers (carrion). Species richness was similar between traps baited with pig, cattle, and elephant dung but was relatively lower in those baited with sheep dung and carrion. In traps baited with pig dung, abundance was relatively greater than in all other bait types. A cluster analysis of species abundance distributions for the 30 most abundant species identified four different patterns of bait type association at a 60% level of similarity. All but 1 of the 15 species in cluster A were attracted primarily to the dung of omnivores and pad-dropping ruminant herbivores (pig and cattle). All seven species of cluster B were attracted primarily to coarse-fibered, nonruminant herbivore dung (elephant). All four species of cluster C were primarily carrion and pig dung associated, whereas all four species of cluster D were carrion specialists. In conclusion, the most abundant species were attracted to all bait types, but most species were largely specialized to different dung types or carrion, with dung attracting the majority of the fauna in terms of both species richness and abundance.     

Orchids of the West Indies: predictability of diversity and endemism

Aim We examined phytogeographical patterns of West Indian orchids, and related island area and maximum elevation with orchid species richness and endemism. We expected strong species–area relationships, but that these would differ between low and montane island groups. In so far as maximum island elevation is a surrogate for habitat diversity, we anticipated a strong relationship with maximum elevation and both species richness and endemism for montane islands. Location The West Indies. Methods Our data included 49 islands and 728 species. Islands were classified as either montane (≥ 300 m elevation) or low (< 300 m). Linear and multivariate regression analyses were run to detect relationships between either area or maximum island elevation and species richness or the number of island endemic species. Results For all 49 islands, the species–area relationship was strong, producing a z‐value of 0.47 (slope of the regression line) and explaining 46% of the variation. For 18 relatively homogeneous, low islands we found a non‐significant slope of z = −0.01 that explained only 0.1% of the variation. The 31 montane islands had a highly significant species–area relationship, with z = 0.49 and accounting for 65% of the variation. Species numbers were also strongly related to maximum island elevation. For all islands < 750 km², we found a small‐island effect, which reduced the species–area relationship to a non‐significant z = 0.16, with only 5% of the variation explained by the model. Species–area relationships for montane islands of at least 750 km² were strong and significant, but maximum elevation was the best predictor of species richness and accounted for 79% of the variation. The frequency of single‐island endemics was high (42%) but nearly all occurred on just nine montane islands (300 species). The taxonomic distribution of endemics was also skewed, suggesting that seed dispersability, while remarkable in some taxa, is very limited in others. Montane island endemics showed strong species–area and species–elevation relationships. Main conclusions Area and elevation are good predictors of orchid species diversity and endemism in the West Indies, but these associations are driven by the extraordinarily strong relationships of large, montane islands. The species richness of low islands showed no significant relationship with either variable. A small‐island effect exists, but the montane islands had a significant relationship between species diversity and maximum elevation. Thus, patterns of Caribbean orchid diversity are dependent on an interplay between area and topographic diversity.     

Biogeographical determinants for total and endemic species richness in a continental archipelago

We examined the relationship between plant species richness and biogeographical variables (island area, island maximum elevation, distance from nearest inhabited island, distance from nearest mainland) using a data set comprising 201 islands of the Aegean archipelago. We found that endemic species richness was strongly correlated to total species richness. Single-island endemic species richness was most strongly correlated to island maximum elevation, and then to island area, with an apparent small island effect for islands smaller than 47 km². Total species richness was most strongly correlated to island area (with no apparent small island effect), and less strongly correlated to island maximum elevation. Distance from the mainland or other inhabited islands displayed limited predictive value in our data set. The slope of the relationship between species richness and geographical factors (island area, elevation, distance from island/mainland) was steeper for endemic species richness than for total richness. Finally, the different scales of endemicity (single-island endemics, island group endemics and Aegean regional endemics) displayed similar qualitative trends and only differed quantitatively. Thus, we conclude that different biogeographical factors act as drivers for total species richness than for endemic species richness.     

Effects of carrion decomposition on litter arthropod assemblages

1. Many organisms contribute to the decomposition of carrion. For arthropods, many studies focus on the necrophagous community, those directly consuming carrion.
2. Necrophagous arthropods use carrion as a shelter or food source. Therefore, carrion generally increases the abundance and biodiversity of necrophagous species. However, it is unclear if carrion has similar effects on detrital communities.
3. This study examines changes in community structure and composition of necrophilous and detrital communities over the course of decomposition.
4. Five pig head carrion were placed at least 7 m apart under cages in temperate mixed forest. Leaf litter was sampled 0 m, 1.5 m, and 3 m from each carrion weekly during summer, and monthly during autumn, until the first frost. Arthropods were extracted from leaf litter by using Berlese funnels.
5. At the carrion site, necrophagous insects increased in abundance, species richness, and Shannon diversity during decomposition, and all decreased after dry decay.
6. Detritus arthropods displayed a sharp increase in abundance during advanced decay, decreasing during dry decay, and a general increase over time for species richness and diversity.
7. In conclusion, carrion can influence the surrounding, non-necrophagous arthropod community, highlighting the need to investigate carrion effects beyond typical necrophagous species to have a more holistic understanding of carrion ecology.

     

Decomposition rate of carrion is dependent on composition not abundance of the assemblages of insect scavengers

Environmental factors and biodiversity affect ecosystem processes. As environmental change modifies also biodiversity it is unclear whether direct effects of environmental factors on ecosystem processes are more important than indirect effects mediated by changes in biodiversity. High-quality resources like carrion occur as heterogeneous pulses of energy and nutrients. Consequently, the distribution of scavenging insects is related to resource availability. Therefore, carrion decomposition represents a suitable process from which to unravel direct effects of environmental change from indirect biodiversity-related effects on ecosystem processes. During three field seasons in 2010 we exposed traps baited with small-mammal carrion at 21 sites along a temperature gradient to explore the insect carrion fauna and decomposition rate in the Bohemian Forest, Germany. The abundance component of beetle and fly assemblages decreased with decreasing temperature. Independently, the composition component of both taxa changed with temperature and season. The change in the composition component of beetles depicted a loss of larger species at higher temperatures. Decomposition rate did not change directly along the temperature gradient but was directly influenced by season. The composition component of beetles, and to a small extent of flies, but not their abundance component, directly affected carrion decomposition. Consequently, lower decomposition rates at lower temperatures can be explained by the absence of larger beetle species. Thus, we predict that future environmental change will modify carrion fauna composition and thereby indirectly decomposition rate. Moreover, reorganizations of the insect carrion composition will directly translate into modified decomposition rates, with potential consequences for nutrient availability and carbon storage.     

Prairie dog towns as islands: applications of island biogeography and landscape ecology for conserving nonvolant terrestrial vertebrates

Aim To evaluate the utility of island biogeography theory as a model for understanding and conserving native communities of nonvolant terrestrial vertebrates at prairie dog towns. Location Oklahoma Panhandle, USA. Methods We surveyed mammal, reptile and amphibian communities on 36 black‐tailed prairie dog (Cynomys ludovicianus) towns during the summers and falls of 1997 to 1999. We used a Geographic Information System (GIS) to characterize the landscape within 10 km of each town. We used Principal Components Analysis (PCA), Correlation Analysis, and Linear Regression to test for patterns in species richness relative to area and isolation of towns, local habitat characteristics, and characteristics of the adjacent landscape. Results Species richness was not significantly correlated with town size, town isolation, or local habitat characteristics. On the other hand, species richness was significantly correlated with characteristics of the landscape within 10 km of the focal town. In addition, species richness of mammals at prairie dog towns during the summer increased in a northerly direction, while richness of mammals at towns during fall increased to the west. Main conclusions These results, albeit contrary to traditional island biogeography theory, are consistent with an emerging view that communities on relatively small islands are strongly influenced by characteristics of the adjacent landscape (or seascape). We recommend that to the extent possible, networks of reserves for prairie dogs and their associated species should include clusters of large towns (i.e. larger than those studied here), as well as large but isolated towns, and that conservation efforts should include management of the intervening matrix of anthropogenic habitats.     

Oviposition preferences and antennal size in carrion flies

Carrion-feeding flies use odours emanating from the decomposing corpse as cues for oviposition and are described as generalists because the larvae feed on the corpses of diverse species. Whereas several features of the corpse may influence the oviposition choices of these flies, it is not known whether there is a preference for a particular species of corpse. We provided carrion flies with ovipositional (and feeding) choices in a field experiment, in which various odour sources were presented simultaneously. We found novel evidence of broadly consistent choices of carrion by flies from four families. Traps baited with decaying fish flesh captured the greatest number of individuals, whereas traps baited with decaying pig liver typically attracted the least. We also asked whether individuals captured in the various baits vary in antennal size, perhaps reflecting different capacities for odour detection. There was a trend for individuals of Lucilia sericata Meigen (Diptera: Calliphoridae) and the platystomatid collected from the traps baited with pig liver to have significantly larger antennae, whereas individuals of Muscina stabulans (Fallen) (Diptera: Muscidae) captured in traps baited with marine fish flesh had relatively longer antennae for their body size. Our data reveal a more nuanced pattern of oviposition behaviour in these generalist carrion flies, which may reflect differences in their preference of carrion with different nutrients, and in their capacity to detect particular odours.     

Do forest plants conform to the theory of island biogeography: the case study of bog islands

Biodiversity conservation is confronted with increasing risk of extinction in isolated small-area remnants and the limitation of species to colonize recently formed habitats. We hypothesized that the equilibrium pattern of forest herb layer in long-term fragmented landscape should comply with the theory of island biogeography. Forests on mineral soil islands located in large mires of western Estonia were considered as dispersal target habitats, and forests on mainland and peninsulas in mires as sources. Species richness was the lowest in mainland forests and the effect was confounded by habitat structure, suggesting a negative effect of silvicultural management in easily accessible forests. We observed the ‘small island effect’, i.e. greater overall species richness in small-area habitats, which was determined by the habitat preference of shade tolerant generalists. The average species richness of common mainland forest specialists varied little, but capitalizing on the traditional approach and analyzing only island data, weak effects of distance and habitat quality were detected. At single species level, unexpectedly, many habitat specialists were observed to have successfully dispersed to islands, indicating insufficient knowledge of the long-distance dispersal mechanisms of forest-dwelling plants. In fragmented forest landscapes the theory of island biogeography can be applied to habitat specialist plant species, but only regarding the effect of isolation and in conditions of persistent forest structural quality. In the light of global changes, optimized conservation planning should primarily target on (i) the conservation of ancient habitat fragments independent of their current area, and (ii) the promotion of diversity of potential dispersal vectors in the landscape.