Climate change effects on behavioral and physiological ecology of predator–prey interactions: Implications for conservation biological control

Habitat management under the auspices of conservation biological control is a widely used approach to foster conditions that ensure a diversity of predator species can persist spatially and temporally within agricultural landscapes in order to control their prey (pest) species. However, an emerging new factor, global climate change, has the potential to disrupt existing conservation biological control programs. Climate change may alter abiotic conditions such as temperature, precipitation, humidity and wind that in turn could alter the life-cycle timing of predator and prey species and the behavioral nature and strength of their interactions. Anticipating how climate change will affect predator and prey communities represents an important research challenge. We present a conceptual framework—the habitat domain concept—that is useful for understanding contingencies in the nature of predator diversity effects on prey based on predator and prey spatial movement in their habitat. We illustrate how this framework can be used to forecast whether biological control by predators will become more effective or become disrupted due to changing climate. We discuss how changes in predator–prey interactions are contingent on the tolerances of predators and prey species to changing abiotic conditions as determined by the degree of local adaptation and phenotypic plasticity exhibited by species populations. We conclude by discussing research approaches that are needed to help adjust conservation biological control management to deal with a climate future.     

Habitat manipulation preferred by Eld’s Deer in Hainan Island,China

In order to improve the conservation status of the Eld’s Deer (Cervus eldii), a critically endangered species in China, a population in a nature reserve on Hainan Island was studied. Abundances and behaviours in two different habitat types, natural and manipulated, were recorded. We found that different habitats were preferred according to season. Both sexes were more abundant in the manipulated habitat from January to May, with males being more abundant in the natural habitat from September to October. However, females, were significantly more abundant from April and May in the manipulated habitat. The deer preferred the more open manipulated habitat for feeding, consistent with greater food availability. This study provides useful evidence for managers to create seasonally suitable habitat for the conservation of this species on Hainan Island. Similar methods could also be applied to other deer species in China, most of which are facing critical survival challenges.     

Central Place Foraging in Nonpatchy Habitats

This paper deal with a model of optimal foraging in a habitat with arbitrary food distribution. It takes into account an arbitrary risk cost related to the distance to the animal's nest. Food acquisition and risk cost are accounted for in common units of fitness. The resulting problem is solved in the context of Calculus of Variations. The optimal duration of absence from the nest and the optimal spatial allocation of foraging time are obtained: the optimal strategy leads to separate the habitat into a region to exploit and a region to ignore. The definition of these two distinct regions depends on the relative importance of risk and food availability. With realistic risk costs, the resulting strategy indicates a highly selective behaviour when far from the nest, as observed in field studies. The model is also extended to take account of the need of returning to the nest to guard it or to feed the young.     

An improved approach to evaluate car sharing options

We develop an improved approach to evaluate car sharing options under uncertain environments with the combination of Fuzzy Analytic Hierarchy Process (F-AHP) and Fuzzy Technique for Order Preference by Similarity to Ideal Solution (F-TOPSIS), which consists of three steps. In the first step, we propose a SCUMN (Specific, Comprehensive, Understandable, Measurable, and Neutral) methodology to identify appropriate indicators and obtain a final list of 24 indicators according to their relevance to car sharing options. In the second step, we determine the weight of each indicator with F-AHP and conduct consistency check of the comparison matrix of selected indicators. In the third step, comparison of different options is performed with selected indicators and F-TOPSIS. A case study is provided to validate the proposed approach. Twenty-four indicators are identified to evaluate five different car sharing options and rank them according to their closeness coefficients in decreasing order. And thirty-one sensitivity analysis experiments are conducted to figure out the influence of indicators on decision making. The experimental results show that the proposed approach is capable of evaluating car sharing options with uncertainty and vagueness. F-AHP is able to determine the weight for each selected indicator and F-TOPSIS demonstrates its advantage in comparing potential options.     

Experimentally induced helper dispersal in colonially breeding cooperative cichlids

The ‘benefits of philopatry’ hypothesis states that helpers in cooperatively breeding species derive higher benefits from remaining home, instead of dispersing and attempting to breed independently. We tested experimentally whether dispersal options influence dispersal propensity in the cooperatively breeding Lake Tanganyika cichlids Neolamprologus pulcher and N. savoryi. Cooperative groups of these fishes breed in densely packed colonies, surrounded by unoccupied, but apparently suitable breeding habitat. Breeding inside colonies and living in groups seems to benefit individuals, for example by early detection and deterrence of predators. We show that despite a slight preference of both species for habitat with a higher stone cover, 40% of the preferred habitat remained unoccupied. On average, the colonies contained a higher number of (1) predators of adults, juveniles and eggs, (2) shelter competitors, and (3) other species including potential food competitors, compared to the outside colony habitat. Apparently, habitat differences cannot explain why these cichlids breed in colonies. Accordingly, dispersal may not be limited by a lack of suitable breeding shelters, but by the relatively higher risk of establishing an outside- compared to a within-colony breeding territory. To test whether cichlids prefer within- to outside-colony breeding territories, we provided breeding shelters inside the colony and at the colony edge and studied helper dispersal. As expected, significantly more shelters were occupied within the colony compared to the edge. New breeding pairs with several helpers occupied these shelters. We conclude that although breeding habitat is plentiful outside the colonies, helpers delay dispersal to obtain a higher quality breeding position within the group or colony eventually, or they disperse in groups. Our results suggest that (1) group augmentation and Allee effects are generally important for dispersal decisions in cooperatively breeding cichlids, consistent with the ‘benefits of philopatry hypothesis’, and (2) habitat saturation cannot fully explain delayed dispersal in these species.     

Bloodmeal analysis in Culicoides midges collected near horses,donkeys and zebras in the Eastern Cape,South Africa

An upsurge in African horse sickness (AHS) in the Eastern Cape, South Africa, from 2006 led to an epidemiological reassessment of the disease there. Light trapping surveys carried out near horses, donkeys and zebras in 2014–2016 collected 39 species of Culicoides midge (Diptera: Ceratopogonidae) that are potential vectors of AHS. To establish if these midges fed on equids, DNA sequences were obtained from the gut contents of 52 female midges (35 freshly blood‐fed, 13 gravid and four parous), representing 11 species collected across 11 sites. Culicoides leucostictus fed on all three equids. Culicoides bolitinos, Culicoides imicola and Culicoides magnus fed on both horses and donkeys. Culicoides onderstepoortensis fed on donkeys, and Culicoides similis and Culicoides pycnostictus fed on zebras. Bloodmeals from cows, pigs, warthogs, impalas and a domestic dog were also identified in various species, but none of the midges tested had fed on birds. These results contribute to knowledge of the vectorial capacity of several species of Culicoides with regard to AHS in the Eastern Cape and point to potential reservoir hosts, of which donkeys, zebras and domestic dogs have previously been found to harbour AHS. Blood‐fed midges were also obtained throughout winter, indicating the potential for endemic AHS in the province.     

Preference and performance of Lepidoptera varies with tree age in juniper woodlands

1. As trees age, they undergo significant physiological and morphological changes. Nevertheless, tree ontogeny and its impacts on herbivores are often overlooked as determinants of plant–herbivore population dynamics and the strength of plant–herbivore interactions. 2. Juniperus (Cupressaceae) is a dominant, long‐lived conifer that serves as the sole host to a specialised assemblage of caterpillars. Over the past 150 years, several juniper species in western North America have expanded their geographic occupancy at local and regional scales, which has resulted in an increase in the number of immature trees on the landscape. Using assays in the laboratory, the effects of tree ontogeny on caterpillar performance and oviposition preference for two juniper specialist caterpillars, Callophrys gryneus (Lycaenidae) and Glena quinquelinearia (Geometridae), were examined. The study considered whether responses to tree ontogeny were consistent across caterpillar species and juniper host species. 3. Tree age was found to be a reliable predictor of caterpillar performance, with caterpillars developing more quickly and growing larger when fed foliage from young trees. Differences in the phytochemical diversity between foliage from trees of different ages might help to explain observed differences in caterpillar performance. Interestingly, the specialist butterfly, C. gryneus, displayed an oviposition preference for foliage from old‐growth Juniperus osteosperma trees, despite the fact that larvae of this species performed poorly on older trees. 4. It is concluded that young juniper trees are an important resource for the specialised Lepidopteran community and that tree ontogeny is an important component of intraspecific variation, which contributes to the structure of plant–herbivore communities.     

Can landscape properties predict occurrence of grey-sided voles?

There has been a long-term decline in spring and fall numbers of Clethrionomys rufocanus in boreal Sweden in 1971–2005. Previous studies on permanent sampling plots in the centre of 2.5 × 2.5 km landscapes suggested that habitat fragmentation (sensu destruction) could have contributed to the decline. Therefore, we tested these findings in a field study and compared trapping results on the central sampling plots of landscapes with a low degree of fragmentation (LDF) and of “hot spot” type with trapping results in managed forest landscapes with a high degree of fragmentation (HDF). We predicted that C. rufocanus would be more common on the LDF plots. We used our permanent plots supplemented with a new sample of plots, mainly of the rare LDF type, inside or just outside the long-term study area. Very few voles were trapped on both plot types, and no difference was found. However, a subsequent pilot study with trapping in a national park with large areas of pristine, unfragmented forest yielded more voles than in the managed, more fragmented, areas. Consequently, the initial field study data and some other recent data were also re-analysed from a “local patch quality” perspective. This alternative approach revealed the positive importance of large focal patches of forest >60 years old and their content of old-growth (pine) forest (>100 years). Interestingly, at the landscape level, the frequency distribution of patches of forest >60 years old, old-growth (>100 years), and especially of old-growth pine forest (>100 years), relative to the properties of plots with C. rufocanus, suggested that there are few forest patches left that are suitable for C. rufocanus. Our current results suggest that habitat fragmentation cannot be excluded as a contributing cause to the long-term decline of C. rufocanus in boreal Sweden.     

The effects of host plant species on adult oviposition and larval performance of the aphid predator Aphidoletes aphidimyza

1. Although preference–performance relationships in insects are typically studied in a bi-trophic context, it is well known that host plants can affect both the preference and performance of natural enemies of herbivorous insects. 2. This study presents evidence from field and laboratory studies that two species of milkweeds, the putatively less defended Asclepias incarnata and the putatively more defended Asclepias syriaca, differentially affect adult oviposition and larval performance in Aphidoletes aphidimyza, an aphid-feeding predatory midge, independent of aphid density. 3. Host plant species affected predatory fly larvae abundance by a factor of 50 in the field and a factor of 8 in the laboratory. Larval and adult emergence rates in our laboratory studies provided strong evidence for reduced performance on A. syriaca. Oviposition in choice and no-choice settings provided some evidence for preference for A. incarnata, and a potentially suppressive effect of A. syriaca. 4. The results provide limited support for the hypothesis that natural selection can lead to positive correlations between adult oviposition preferences and larval performance upon various food sources, even when predatory insects oviposit onto host plants of their herbivorous prey. 5. Preference and performance are not perfectly aligned in this system, however, because ovipositing females do not reject A. syriaca entirely. Potential explanations for mismatches between preference and performance in this system include the neural constraints associated with being a generalist, adaptive time-limited foraging strategies, and unique evolutionary histories of laboratory colonies compared with wild insects.