Brachytrupes megacephalus Lefèbvre, 1827 (Orthoptera, Gryllidae) in the Maltese Islands: notes on biogeography, behaviour, and habitat of populations in the central Mediterranean area and the Maghreb

Brachytrupes megacephalus (Lefebvre, 1827) is of significant biogeographic importance. It occurs in Sicily and on some of the circum-Sicilian and Pelagian islands, as well as in the Maltese Islands, Sardinia and the Maghreb (notably but not exclusively, in Algeria and Tunisia, where it maintains populations in both coastal and desert regions). Within European territory, it occurs solely in Italy and Malta, where it is protected under the EU Habitats Directive and the Bern Convention. In northern Africa, the species is regarded as a polyphagous pest, particularly in Saharan locations. The present work is based on field observations, mostly from the Maltese Islands, that span more than three decades; it provides insights on spatial distribution, population trends and behaviour. In examining the relationship between the species’ frequency during its mating season and weather conditions, results suggest a weak yet statistically significant correlation between mating strategies and ambient meteorological conditions. Moreover, patch occupancy in spring and autumn varied considerably within a specified area of study, primarily due to competitive mating strategies employed in spring, with an occupancy ratio of approximately 1:6. To-date, the species is known from 13 locations, one in Gozo and 12 in Malta, of which some constitute the Ahrax promontory metapopulation. Connectivity between the Ahrax subpopulation cluster is discussed in the light of habitat and topographical characteristics. Contrasting findings on variances in behaviour between Maltese populations and other populations in Sicily and the Maghreb are discussed. Discernible behavioural disparities include the length of excavated tunnels during spring and summer/autumn seasons in the different geographical locations, attraction to artificial sources of light, and the degree of damage to crops across geographic regions.

Mechanisms of biodiversity between Campylobacter sequence types in a flock of broiler-breeder chickens

ABSTRACTA long-term study of Campylobacter sequence types was used to investigate the competitive framework of the Campylobacter metacommunity, and understand how multiple sequence types simultaneously co-occur in a flock of chickens. A combination of matrix and patch-occupancy models were used to estimate parameters describing the competition, transmission, and mortality of each sequence type. It was found that Campylobacter sequence types form a strong hierarchical framework within a flock of chickens, and occupied a broad spectrum of transmission-mortality trade-offs. Upon further investigation of how biodiversity is thus maintained within the flock, it was found that the demographic capabilities of Campylobacter, such as mortality and transmission, could not explain the broad biodiversity of sequence types seen, suggesting that external factors such as host-bird health and seasonality are important elements in maintaining biodiversity of Campylobacter sequence types.

Factors affecting presence and relative abundance of the Endangered volcano rabbit Romerolagus diazi, a habitat specialist

Habitat specialists are particularly vulnerable to extinction when habitat conditions are altered. Information on the habitat use of such species is thus important because it provides insight into factors that influence distribution and abundance, which is crucial for conservation. Here, we aimed to identify factors that influence the patterns of presence and abundance of the Endangered volcano rabbit Romerolagus diazi, a rare leporid with a patchy distribution. Through exhaustive sampling of its range in the Sierra Chichinautzin and Sierra Nevada volcanic fields, Mexico, and using generalized linear models, we found that the probability of patch occupancy was higher where bunchgrass cover exceeded 75%, rock cover exceeded 5%, no cattle grazing was observed and human settlements were at least 7 km away. Patches with greater relative abundance were those with similar characteristics, but located at elevations > 3,600 m, and with rock cover < 15%. Cattle grazing was identified as a major threat to local populations of the volcano rabbit, particularly in the Sierra Chichinautzin. Because of the significance of bunchgrasses for this species, the protection of the mountain grasslands is required in both volcanic fields.

Dynamic spatio-temporal patterns of metapopulation occupancy in patchy habitats

Spatio-temporal dynamics in habitat suitability and connectivity among mosaics of heterogeneous wetlands are critical for biological diversity and species persistence in aquatic patchy landscapes. Despite the recognized importance of stochastic hydroclimatic forcing in driving wetlandscape hydrological dynamics, linking such effects to emergent dynamics of metapopulation poses significant challenges. To fill this gap, we propose here a dynamic stochastic patch occupancy model (SPOM), which links parsimonious hydrological and ecological models to simulate spatio-temporal patterns in species occupancy in wetlandscapes. Our work aims to place ecological studies of patchy habitats into a proper hydrologic and climatic framework to improve the knowledge about metapopulation shifts in response to climate-driven changes in wetlandscapes. We applied the dynamic version of the SPOM (D-SPOM) framework in two wetlandscapes in the US with contrasting landscape and climate properties. Our results illustrate that explicit consideration of the temporal dimension proposed in the D-SPOM is important to interpret local- and landscape-scale patterns of habitat suitability and metapopulation occupancy. Our analyses show that spatio-temporal dynamics of patch suitability and accessibility, driven by the stochasticity in hydroclimatic forcing, influence metapopulation occupancy and the topological metrics of the emergent wetlandscape dispersal network. D-SPOM simulations also reveal that the extinction risk in dynamic wetlandscapes is exacerbated by extended dry periods when suitable habitat decreases, hence limiting successful patch colonization and exacerbating metapopulation extinction risks. The proposed framework is not restricted only to wetland studies but could also be applied to examine metapopulation dynamics in other types of patchy habitats subjected to stochastic external disturbances.

Porównawcza ocena programów analizy żywotności populacji (PVA) w rankingu scenariuszy przekształceń krajobrazu = A comparative assessment of PVA software packages applied to rank the landscape management scenarios

Because of the scale and speed of species extinctions conservationists require methods that facilitate decision making. Therefore, a wide range of habitat and population viability analysis (PVA) software has been developed. Given the diversity of available programs it is currently challenging to decide which program is the most appropriate for a particular problem and what has to be considered when interpreting and comparing results from different approaches. Previous comparisons of PVA software addressed more generic questions such as data requirements, assumptions and predictive accuracy. In contract, we focus on a more applied problem that is still unresolved: how do simple habitat models and PVA software packages affect the ranking of alternative management scenarios? We addressed this problem by comparing different packages (LARCH, META-X, VORTEX and RAMAS GIS). As a test case, we studied the impact of alternative landscape development scenarios (river regulation, grassland restoration, reforestation and renaturalisation) for the Vistula valley, Poland, on the natterjack toad (Bufo calamita). In this context we also aimed to assess whether the use of at least two different PVA packages can enable users to better understand the differences in model predictions, which would imply a greater awareness and critical use of the packages. Our model selection represents different approaches to population viability analysis, including habitat, local population and stochastic patch occupancy models. The models can be evaluated in regard to the complexity of parameters and to the way the landscape is handled. We used RAMAS GIS to create a habitat model (RAMASh) and a detailed spatially explicit stochastic metapopulation model (RAMASp) which combined served as a complete “virtual” dataset for parameterisation of other programs. As an example of a stochastic patch occupancy model, we selected the META-X software. For a more independent comparison we added VORTEX – another package that includes explicit population dynamics, similar to RAMAS. Additionally, we included the habitat model LARCH because this type of model is often used by policy makers. We compared the metapopulation structure produced by RAMASh and LARCH. Scenario ranking according to the predicted carrying capacity in both programs was exactly the same, because the quantitative results for each scenario were almost identical in both programs. However, the metapopulation structure showed big differences between the programs, especially in the number of small populations. The analyses of results of different PVA programs (RAMASp, VORTEX and META-X) showed that absolute values of viability measures partly differed among these programs. Slight differences in population growth rate in RAMASp and VORTEX were amplified by stochasticity and resulted in visibly lower values of final abundance in VORTEX than in RAMASp. Also the absolute values of intrinsic mean time to extinction showed some discrepancies in VORTEX and META-X. These results are in agreement with findings of previous PVA comparisons, which emphasizes that absolute values of viability measures produced by any single model should be treated with caution. Nevertheless, despite these differences the rankings of the scenarios were the same in all three programs. However the order of the scenarios was different than in habitat models. In addition, these rankings were robust to the choice of viability measure. Taken together, these results emphasize that scenario ranking delivered by PVA software is robust and thus very useful for conservation management. Furthermore, we recommend using at least two PVA software packages in parallel, as this forces user to scrutinize the simplifying assumptions of the underlying models and of the viability metrics used.

Predicting patch occupancy reveals the complexity of host range expansion

Specialized plant-insect interactions are a defining feature of life on earth, yet we are only beginning to understand the factors that set limits on host ranges in herbivorous insects. To better understand the recent adoption of alfalfa as a host plant by the Melissa blue butterfly, we quantified arthropod assemblages and plant metabolites across a wide geographic region while controlling for climate and dispersal inferred from population genomic variation. The presence of the butterfly is successfully predicted by direct and indirect effects of plant traits and interactions with other species. Results are consistent with the predictions of a theoretical model of parasite host range in which specialization is an epiphenomenon of the many barriers to be overcome rather than a consequence of trade-offs in developmental physiology.

Different Species Requirements within a Heterogeneous Spring Complex Affects Patch Occupancy of Threatened Snails in Australian Desert Springs

(1) The distribution of organisms that inhabit patchy systems is dictated by their ability to move between patches, and the suitability of environmental conditions at patches to which they disperse. Understanding whether the species involved are identical to one another in their environmental requirements and their responses to variance in their environment is essential to understanding ecological processes in these systems, and to the management of species whose patchy and limited distributions present conservation risks. (2) Artesian springs in Australia’s arid interior are “islands” of hospitable wetland in uninhabitable “oceans” of dry land and are home to diverse and threatened assemblages of endemic species with severely restricted distributions. Many have strict environmental requirements, but the role of environmental heterogeneity amongst springs has rarely been considered alongside conventional patch characteristics (isolation and patch geometry). (3) We quantified environmental heterogeneity across springs, and the relationship between spring size, isolation (distances to neighbours) and environmental quality (depth, water chemistry), and patterns of occupancy and population persistence of six endemic spring snail species, all from different families, and with all restricted to a single <8000 ha system of springs in Australia. To do so, a survey was conducted for comparison against survey results of almost a decade before, and environmental variables of the springs were measured. Many of the snail species occupied few sites, and environmental variables strongly covaried, so an ordination-based approach was adopted to assess the relationship between environmental measures and the distribution of each species, and also whether springs that held a higher diversity of snails had specific characteristics. (4) Each snail species occupied a subset of springs (between 5% and 36% of the 85 sampled) and was associated with a particular set of conditions. Of the six species considered in further detail, most were restricted to the few springs that were large and deep. Species in family Tateidae were distinct in having colonised highly isolated springs (with >300 m to nearest neighbour). Springs with highest diversity were significantly larger, deeper and had more numerous neighbours within 300 m than those devoid of endemic snails, or those with low diversity. (5) Although spring size and isolation affect patterns of occupancy, the six snail species had significantly different environmental requirements from one another and these correlated with the distribution pattern of each. Approaches that ignore the role of environmental quality—and particularly depth in springs—are overlooking important processes outside of patch geometry that influence diversity. These organisms are highly susceptible to extinction, as most occupy less than 3 ha of habitat spread across few springs, and habitat degradation continues to compromise what little wetland area is needed for their persistence.