Areas Of Co-occurrence Research Articles

A Continental-Scale Connectivity Analysis to Predict Current and Future Colonization Trends of Biofuel Plant’s Pests for Sub-Saharan African Countries

Biofuel production in Sub-Saharan Africa is an important part of local low-income countries. Among many plant species, Jatropha curcas gained popularity in this area, as it can be grown even where crops of agricultural interest cannot. A natural African pest of J. curcas is the Aphthona cookei species group, for which future climatic suitability is predicted to favor areas of co-occurrence. In this research, we identify the possible climatic corridors in which the colonization of J. curcas crops may occur through a circuit theory-based landscape connectivity software at a country scale. Additionally, we use the standardized connectivity change index to predict possible variations in future scenarios. Starting from ecological niche models calibrated on current and 2050 conditions (two different RCP scenarios), we found several countries currently showing high connectivity. Ghana, Zambia and Ivory Coast host both high connectivity and a high number of J. curcas cultivations, which is also predicted to increase in the future. On the other side, Burundi and Rwanda reported a future increase of connectivity, possibly acting as “connectivity bridges” among neighboring countries. Considering the economic relevance of the topic analyzed, our spatially explicit predictions can support stakeholders and policymakers at a country scale in informed territorial management.

Space invaders: effects of invasive alien Pallas’s squirrel on home range and body mass of native red squirrel

Alien species can affect native species through several ecological processes such as competition. Here we tested the hypothesis of interspecific competition for space and food resources between the native Eurasian red squirrel and the invasive Pallas’s squirrel introduced in Italy. We used an experimental study design comparing space and habitat use and body condition parameters of red squirrels between areas of co-occurrence with the Pallas’s squirrel and areas without it. There were no differences in mean home range size of red squirrels between red-only areas and red-Pallas. However, when Pallas’s squirrels were removed, the red squirrels increased their home ranges. Moreover, in the area of syntopy, red squirrels had a higher degree of intraspecific home range overlap than in the red-only area. We also found indirect evidence for competition for food with red squirrels having a poorer body condition when co-occurring with the alien species. We analyzed the body mass and size of red squirrels in the two areas and our results showed that red squirrels had a reduced body mass and size when in syntopy, confirming that the interspecific competition does not allow red squirrels to reach the optimum body condition that they would have if the competitor was not present. Moreover, tree-species niche overlap was very high and both species fed primarily on the same tree seeds. Differences in vegetation cover between areas are discussed. This is the first study that confirms the invasiveness of the Pallas’s squirrel also in terms of capability to compete with native species.

Surreptitious sympatry: Exploring the ecological and genetic separation of two sibling species.

Climate change is having profound impacts on animal populations, and shifts in geographic range are predicted in response. Shifts that result in range overlap between previously allopatric congeneric species may have consequences for biodiversity through interspecific competition, hybridization, and genetic introgression. Harbor seals (Phoca vitulina) and spotted seals (Phoca largha) are parapatric sibling species and areas of co‐occurrence at the edges of their range, such as Bristol Bay, Alaska, offer a unique opportunity to explore ecological separation and discuss potential consequences of increased range overlap resulting from retreating sea ice. Using telemetry and genetic data from 14 harbor seals and six spotted seals, we explored the ecological and genetic separation of the two species by comparing their utilization distributions, distance from haul‐out, dive behavior (e.g., depth, duration, focus), and evidence of hybridization. Firstly, we show that harbor and spotted seals, which cannot be visually distinguished definitively in all cases, haul‐out together side by side in Bristol Bay from late summer to early winter. Secondly, we observed subtle rather than pronounced differences in ranging patterns and dive behavior during this period. Thirdly, most spotted seals in this study remained close to shore in contrast to what is known of the species in more northern areas, and lastly, we did not find any evidence of hybridization. The lack of distinct ecological separation in this area of sympatry suggests that interspecific competition could play an important role in the persistence of these species, particularly if range overlap will increase as a result of climate‐induced range shifts and loss of spotted seal pagophilic breeding habitat. Our results also highlight the added complexities in monitoring these species in areas of suspected overlap, as they cannot easily be distinguished without genetic analysis. Predicted climate‐induced environmental change will likely influence the spatial and temporal extent of overlap in these two sibling species. Ultimately, this may alter the balance between current isolating mechanisms with consequences for species integrity and fitness.

Interspecific competition between alien Pallas’s squirrels and Eurasian red squirrels reduces density of the native species

When alien species introduced into a new environment have a strong niche overlap with ecologically similar native species, interspecific competition can cause a decrease in abundance and distribution of native species. Pallas’s squirrel (Callosciurus erythraeus) was introduced in Northern Italy where it currently co-occurs with native Eurasian red squirrels (Sciurus vulgaris). The alien species is known for its invasiveness but so far negative effects of Pallas’s squirrels on native tree squirrels have not been demonstrated. Here, we compare demographic parameters of red squirrel populations between sites without (red-only sites) and with (red-Pallas’s sites) C. erythraeus and present results of trapping and removal of Pallas’s squirrel and its effects on red squirrel population dynamics. The native species was patchily distributed and absent in many trapping sites occupied by the Pallas’s squirrel. Red squirrels occurred at much lower densities and showed reduced adult survival in areas of co-occurrence than in red-only sites, but there were no differences in reproductive rate. Removing invasive squirrels throughout the study period resulted in re-colonisation by the native species only in some trapping sites, and several alternatives to explain the lack of a marked increase in population size are discussed. This study is the first to provide evidence that presence of Pallas’s squirrel reduces viability of local red squirrel populations.

Comparative morpho-physiological analysis between Ciona robusta and Ciona savignyi

The seasquirt Ciona robusta and its co-generic Ciona savignyi, are two long-divergent species, sharing the same habitat and competing for the same spaces and resources. Their very similar morphology has been responsible for the misidentification of the two organisms, and, consequently, for the underestimation of their geographic distributions and new areas of co-occurrence. In spite of the large amount of knowledge built up by developmental biologists, few data are available regarding the morpho-physiology of the two sea squirts. The comparison of morphological and physiological features carried out in the present study (i.e. length-body weight correlation, tunic/organ ratio, tissue-specific retained water and metabolic rate), highlighted slight, but significant, differences strongly supporting the hypothesis of different ecological strategies for the two species. More precisely, C. savignyi invests more energy in growing faster and taller, likely to improve the quality and concentration of the filtered food, and sustains a faster metabolic/growth rate. Conversely, C. robusta invests more into tunic thickness, reducing the risk of predation, even if this likely means a slower metabolic/growth rate. In addition it was noted that in both species, the tunic absorbs more water than the other tissues, a peculiarity that may allow them to better counteract sudden fluctuations in environmental salinity.

Niche partitioning at the edge of the range: a multidimensional analysis with sympatric martens

The structure of mesopredators’ communities is complex and results from a multidimensional web of interactions such as top-down and bottom-up regulation or intraguild interactions. However, these interactions may change geographically along species’ distribution ranges. The pine marten ( Martes martes ) and stone marten ( Martes foina ) are 2 similar-sized mustelids with overlapping ecological traits and a wide distribution overlap. The absence of stone martens from potentially adequate areas has been advocated as resulting from competitive exclusion by pine martens. Particularly, the preference of both species for mammalian rodents could be the main driver of such competitive stress. However, their elusive behavior and morphological similarity of their scats often precluded the evaluation of their ecological traits in areas of co-occurrence. Using camera trapping and diet analysis on genetically identified scats, we evaluated the interactions between pine and stone martens in the southwestern limit of their range along 3 ecological niche dimensions: spatial, trophic, and temporal, under a hypothesis of competitive dominance of pine martens. We found no spatial segregation, and that coexistence was facilitated by seasonally adjusted shifts along the trophic and temporal axes. While both species often co-occurred, during the season of low food resources, pine martens exploited the less profitable feeding resource. Moreover, they not only displayed an activity pattern that limited their access to rodents, but also reduced the probabilities of direct encounters with stone martens. We suggest that the dominance position has changed in favor of the stone marten in our study area, probably as a result of habitat quality and range edge effects. These findings support the relative instability of interspecific interactions among similar-sized species, which should be evaluated using multidimensional and site-specific approaches.

Stable isotope patterns of benthic organisms from the Great Lakes region indicate variable dietary overlap of Diporeia spp. and dreissenid mussels

Competition between native and invasive species may bring about a suite of ecological and evolutionary outcomes, including local extirpations. In the Laurentian Great Lakes, competition for food may explain the dramatic decline of Diporeia spp. amphipods following the introduction of dreissenid mussels. This hypothesis has not been confirmed, in part because dreissenids and Diporeia appear to co-exist and flourish in other systems, including the Finger Lakes of New York. We used carbon, nitrogen, hydrogen, and oxygen stable isotope ratios to examine resource use by Diporeia from three spatially distinct populations (Lake Michigan, Lake Superior, and Cayuga Lake), dreissenids from areas where they co-occur with Diporeia (Lake Michigan and Cayuga Lake), and Diporeia from Lake Michigan collected before and after dreissenid invasion (1986–2009). Our results suggest that dreissenids may affect resource use by Diporeia in areas of co-occurrence, but the extent to which those effects are positive or negative is unclear. Terrestrial inputs may provide an important subsidy for Diporeia populations in small systems but may not be substantial enough in the Great Lakes to ensure that both taxa thrive.

Changes in the distribution of multispecies pest assemblages affect levels of crop damage in warming tropical Andes.

Climate induced species range shifts might create novel interactions among species that may outweigh direct climatic effects. In an agricultural context, climate change might alter the intensity of competition or facilitation interactions among pests with, potentially, negative consequences on the levels of damage to crop. This could threaten the productivity of agricultural systems and have negative impacts on food security, but has yet been poorly considered in studies. In this contribution, we constructed and evaluated process-based species distribution models for three invasive potato pests in the Tropical Andean Region. These three species have been found to co-occur and interact within the same potato tuber, causing different levels of damage to crop. Our models allowed us to predict the current and future distribution of the species and therefore, to assess how damage to crop might change in the future due to novel interactions. In general, our study revealed the main challenges related to distribution modeling of invasive pests in highly heterogeneous regions. It yielded different results for the three species, both in terms of accuracy and distribution, with one species surviving best at lower altitudes and the other two performing better at higher altitudes. As to future distributions our results suggested that the three species will show different responses to climate change, with one of them expanding to higher altitudes, another contracting its range and the other shifting its distribution to higher altitudes. These changes will result in novel areas of co-occurrence and hence, interactions of the pests, which will cause different levels of damage to crop. Combining population dynamics and species distribution models that incorporate interspecific trade-off relationships in different environments revealed a powerful approach to provide predictions about the response of an assemblage of interacting species to future environmental changes and their impact on process rates.

The importance of conflict-induced mortality for conservation planning in areas of human–elephant co-occurrence

• We model effects of conflict-induced mortality and core area loss on populations. • We evaluate if human–wildlife conflict devalues co-occurrence areas. • Decreased inviolate core accelerates negative effects of human–wildlife conflict. • Interaction of core area loss and conflict result in extinction thresholds. • Conflict mitigation is essential for conservation in co-occurrence areas. Multiple-use zones around protected areas are designed to balance human resource needs with wildlife conservation, but conflicts between wildlife and people in these areas of co-occurrence (CA) can seriously undermine their conservation potential. We evaluated this issue by assessing the effects of conflict-induced mortality in CAs around an inviolate core, on long-term population viability of the endangered, wide-ranging, and conflict-prone Asian elephant ( Elephas maximus ). Using a single-sex, age-structured density-dependent matrix population model to simulate elephant population dynamics over a period of 500 years, we: (1) assessed the existence of extinction thresholds arising from the interaction of mortality due to human–elephant conflict (HEC) and habitat degradation, and (2) evaluated whether and to what extent habitat supplementation by the CA is devalued by detrimental effects of conflict-induced mortality. We parameterized our model using published survival and fecundity rates. We considered different scenarios of core to CA configurations, and simulated the population under HEC-induced mortality rates ( HECm ) ranging from 0 to 0.1. Population persistence was adversely affected by HECm , and its detrimental effects were magnified as the proportion of core habitat declined. Under moderate HECm , small increments in mortality rates necessitated disproportionately large increases in core area availability to avoid quasi-extinction. Furthermore, benefits of CA supplementation were driven more by CA quality than size, and these benefits declined as HECm increased. We emphasize the need to minimize conflict-induced mortality, or to maintain adequate refugia from such anthropogenic threats, to successfully conserve conflict-prone species in human-dominated landscapes.

Why do species co-occur? A test of alternative hypotheses describing abiotic differences in sympatry versus allopatry using spadefoot toads.

Areas of co-occurrence between two species (sympatry) are often thought to arise in regions where abiotic conditions are conducive to both species and are therefore intermediate between regions where either species occurs alone (allopatry). Depending on historical factors or interactions between species, however, sympatry might not differ from allopatry, or, alternatively, sympatry might actually be more extreme in abiotic conditions relative to allopatry. Here, we evaluate these three hypothesized patterns for how sympatry compares to allopatry in abiotic conditions. We use two species of congeneric spadefoot toads, Spea multiplicata and S. bombifrons, as our study system. To test these hypotheses, we created ecological niche models (specifically using Maxent) for both species to create a map of the joint probability of occurrence of both species. Using the results of these models, we identified three types of locations: two where either species was predicted to occur alone (i.e., allopatry for S. multiplicata and allopatry for S. bombifrons) and one where both species were predicted to co-occur (i.e., sympatry). We then compared the abiotic environment between these three location types and found that sympatry was significantly hotter and drier than the allopatric regions. Thus, sympatry was not intermediate between the alternative allopatric sites. Instead, sympatry occurred at one extreme of the conditions occupied by both species. We hypothesize that biotic interactions in these extreme environments facilitate co-occurrence. Specifically, hybridization between S. bombifrons females and S. multiplicata males may facilitate co-occurrence by decreasing development time of tadpoles. Additionally, the presence of alternative food resources in more extreme conditions may preclude competitive exclusion of one species by the other. This work has implications for predicting how interacting species will respond to climate change, because species interactions may facilitate survival in extreme habitats.

POSITIVE FEEDBACK BETWEEN ECOLOGICAL AND REPRODUCTIVE CHARACTER DISPLACEMENT IN A YOUNG AVIAN HYBRID ZONE

Character displacement can reduce costly interspecific interactions between young species. We investigated the mechanisms behind divergence in three key traits-breeding habitat choice, timing of breeding, and plumage coloration-in Ficedula flycatchers. We found that male pied flycatchers became expelled from the preferred deciduous habitat into mixed forest as the superior competitor, collared flycatchers, increased in numbers. The peak in food abundance differs between habitats, and the spatial segregation was paralleled by an increased divergence in timing of breeding between the two species. Male pied flycatchers vary from brown to black with brown coloration being more frequent in sympatry with collared flycatchers, a pattern often proposed to result from selection against hybridization, that is, reinforcement. In contrast to this view, we show that brown male pied flycatchers more often hybridize than black males. Male pied flycatcher plumage coloration influenced the territory obtained in areas of co-occurrence with collared flycatchers, and brown male pied flycatchers experienced higher relative fitness than black males when faced with heterospecific competition. We suggest that allopatric divergence in resource defense ability causes a feedback loop at secondary contact where male pied flycatchers with the most divergent strategy compared to collared flycatchers are favored by selection.

Hard traits of three Bromus species in their source area explain their current invasive success

We address two highly essential question using three Eurasian Bromus species with different invasion success in North America as model organisms: (1) why some species become invasive and others do not, and (2) which traits can confer pre-adaptation for species to become invasive elsewhere. While the morphology and phenology of the chosen bromes ( Bromus tectorum, Bromus sterilis and Bromus squarrosus) are highly similar, we measured complex traits often associated with invasive success: phenotypic plasticity, competitive ability and generalist-specialist character. We performed common-garden experiments, community- and landscape-level surveys in areas of co-occurrence in Central Europe (Hungary) that could have served as donor region for American introductions. According to our results, the three bromes are unequally equipped with trait that could enhance invasiveness. B. tectorum possesses several traits that may be especially relevant: it has uniquely high phenotypic plasticity, as demonstrated in a nitrogen addition experiment, and it is a habitat generalist, thriving in a wide range of habitats, from semi-natural to degraded ones, and having the widest co-occurrence based niche-breadth. The strength of B. sterilis lies in its ability to use resources unexploited by other species. It can become dominant, but only in one non-natural habitat type, namely the understorey of the highly allelopathic stands of the invasive Robinia pseudoacacia. B. squarrosus is a habitat specialist with low competitive ability, always occurring with low coverage. This ranking of the species’ abilities can explain the current spreading success of the three bromes on the North American continent, and highlight the high potential of prehistoric invaders (European archaeophytes) to become invasive elsewhere.

Gambling, alcohol, consumption, cigarette smoking and health: Findings from the 2007 British Gambling Prevalence Survey

Previous research has shown an association between gambling, alcohol and cigarette smoking. Co-occurrence of problem gambling with other behavioural and psychological disorders can exacerbate, or be exacerbated by, problem gambling. Using participant data from the 2007 British Gambling Prevalence Survey (n = 9003 adults aged 16 years and above), secondary analysis was carried out on the relationship between gambling and three particular areas of co-occurrence. These were general health status, cigarette smoking and alcohol consumption. All analysis was age standardised to allow comparisons between groups after adjusting for the effects of any difference in their age distributions. Results showed that: (i) cigarette smokers were significantly more likely to gamble in the past year compared to non-smokers, (ii) cigarette smokers were over three times more likely than non-smokers to be a problem gambler, (iii) alcohol consumption as measured by the number of units drunk on the person's heaviest drinking day was not significantly associated with having gambled in the past year, (iv) alcohol consumption as measured by the number of units drank on the person's heaviest drinking day in the past year was significantly associated with problem gambling, (v) health status was not significantly associated with past year gambling and (vi) the prevalence rate of problem gambling among those with poor health were over three times as likely to be a problem gambler compared to those with good health. Implications of these results are discussed.

A species delimitation approach in the Trochulus sericeus/hispiduscomplex reveals two cryptic species within a sharp contact zone

BackgroundMitochondrial DNA sequencing increasingly results in the recognition of genetically divergent, but morphologically cryptic lineages. Species delimitation approaches that rely on multiple lines of evidence in areas of co-occurrence are particularly powerful to infer their specific status. We investigated the species boundaries of two cryptic lineages of the land snail genus Trochulus in a contact zone, using mitochondrial and nuclear DNA marker as well as shell morphometrics.ResultsBoth mitochondrial lineages have a distinct geographical distribution with a small zone of co-occurrence. In the same area, we detected two nuclear genotype clusters, each being highly significantly associated to one mitochondrial lineage. This association however had exceptions: a small number of individuals in the contact zone showed intermediate genotypes (4%) or cytonuclear disequilibrium (12%). Both mitochondrial lineage and nuclear cluster were statistically significant predictors for the shell shape indicating morphological divergence. Nevertheless, the lineage morphospaces largely overlapped (low posterior classification success rate of 69% and 78%, respectively): the two lineages are truly cryptic.ConclusionThe integrative approach using multiple lines of evidence supported the hypothesis that the investigated Trochulus lineages are reproductively isolated species. In the small contact area, however, the lineages hybridise to a limited extent. This detection of a hybrid zone adds an instance to the rare reported cases of hybridisation in land snails.

Genetic relationships and variation in reproductive strategies in four closely related bromeliads adapted to neotropical ‘inselbergs’: Alcantarea glaziouana, A. regina, A. geniculata and A. imperialis (Bromeliaceae)

Bromeliads (Bromeliaceae) adapted to rock outcrops or 'inselbergs' in neotropical rain forests have been identified as suitable plant models for studying population divergence and speciation during continental plant radiations. Little is known about genetic relationships and variation in reproductive strategies within and among inselberg-adapted species, yet knowledge of these parameters is important for understanding divergence processes and for conservation planning. Nuclear microsatellites were used to assess the role of clonal reproduction, estimate genetic diversity and explore genetic relationships and variation in reproductive strategies for a total of 15 populations of four closely related Alcantarea inselberg species in south-eastern Brazil: A. glaziouana, A. regina, A. geniculata and A. imperialis. Clonal propagation is frequent in coastal populations of A. glaziouana and A. regina, but absent in the high-altitude species A. geniculata and A. imperialis. Considerable variation in clonal diversity, gene diversity (H(e)), allelic richness, and Wright's inbreeding coefficient (F(IS)) exists within and between species of Alcantarea. A Bayesian analysis of coastal inselberg species indicated pronounced genetic structure. A neighbor-joining analysis grouped populations of each species together with moderate bootstrap support, except for the high altitude species A. imperialis. The coastal inselberg species A. glaziouana and A. regina tend to propagate asexually via vegetative clonal growth, and both reproductive strategies and breeding systems vary greatly between populations and species of Alcantarea. The microsatellite data indicate a history of hybridization and reticulation involving the high-altitude species A. geniculata and A. imperialis in areas of co-occurrence. The results highlight the need to understand similarities and differences in reproductive strategies both within and between related species for conservation planning and as a basis for understanding evolutionary processes in tropical radiations.

Aethomys ineptus (Rodentia: Muridae)

Aethomys ineptus (Thomas and Wroughton, 1908), commonly called the Tete veld rat, is a medium-sized rodent with a long, sparsely haired tail and spermatozoa with spatulate-shaped heads (unique for all muroid rodents thus far examined). A. ineptus co-occurs with its sibling species, A. chrysophilus, and in areas of co-occurrence, an examination of spermatozoa, diploid number, allozymes, or mitochondrial DNA is required to distinguish the 2. Previous work described as many as 11 species of Aethomys, but recent evidence indicates a need for taxonomic revision of the genus. Endemic to Africa, A. ineptus prefers habitats where there is substantial cover in the form of shrubs, rocks, and herbaceous vegetation. It is not of special conservation concern. DOI: 10.1644/809.1.

Aethomys chrysophilus (Rodentia: Muridae)

Abstract The genus Aethomys currently includes 11 species, but recent evidence indicates a need for taxonomic revision of the genus. Aethomys chrysophilus (De Winton, 1897) is a muroid rodent commonly called the red veld rat. A medium-sized rodent with a long, sparsely haired tail, A. chrysophilus is largely parapatric with its sibling species, A. ineptus, and in areas of co-occurrence, determination of chromosome number, mitochondrial DNA analysis, or morphology of spermatozoa are required to distinguish A. chrysophilus from A. ineptus. Endemic to Africa, A. chrysophilus is found in savanna–woodland habitats that include varying combinations of grass–herbaceous ground cover, shrub understory, and miombo or mopane woodlands. It is not of special conservation concern.

Distribution patterns and selective feeding in two Astropecten species (Asteroidea:Echinodermata) from Cleveland Bay, northern Queensland

During 1985, Astropecten zebra was concentrated in shallow inshore areas of Cleveland Bay, northern Queensland, Australia, whereas Astropecten velitaris was found only further offshore. The two species had an overlapping distribution in depths between 5 and 13 m, but juveniles (maximum arm length ≤ 16 mm) were virtually absent from areas of co-occurrence: A. zebra juveniles were largely restricted to inshore areas, whereas A. velitaris juveniles were predominantly found in offshore areas. Analysis of stomach contents demonstrated that both species are selective feeders, consuming mainly bivalves and gastropods, which constituted nearly 90% of the diet in A. zebra and nearly 75% in A. velitaris. The diet of the latter is complemented largely by crustaceans (17.1%). Crustaceans were proportionately better represented in the stomach contents of A. velitaris than in bottom samples. In contrast, although foraminiferans and polychaetes dominated the bottom samples, they were virtually absent from the stomach contents of either species of Astropecten. Both species demonstrated a preference for small prey items. Although spatial differences in the diet of A. velitaris were observed, there was little evidence for competitive interactions. The findings strengthen the view that there is a clear horizontal zonation in benthic communities of the Great Barrier Reef Marine Park, requiring an appropriate management strategy.