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opencc-zeroDec 2016View details →

Data from: Specialists and generalists coexist within a population of spider-hunting mud dauber wasps

Individual foraging specialization describes the phenomenon where conspecifics within a population of generalists exhibit differences in foraging behavior, each specializing on different prey types. Individual specialization is widespread in animals, yet is understudied in invertebrates, despite potential impacts to food web and population dynamics. Sceliphron caementarium (Hymenoptera: Sphecidae) is an excellent system to examine individual specialization. Females of these mud-dauber wasps capture and paralyze spiders which they store in mud nests to provision their offspring. Individuals may make hundreds of prey choices in their short lifespan and fully intact prey items can be easily excavated from their mud nests, where each distinct nest cell represents a discrete foraging bout. Using data collected from a single population of S. caementarium (where all individuals had access to the same resources), we found evidence of strong individual specialization; individuals utilized different resources (with respect to prey taxa, prey ecological guild, and prey size) to provision their nests. The extent of individual specialization differed widely within the population with some females displaying extreme specialization (taking only prey from a single species) while others were generalists (taking prey from up to six spider families). We also found evidence of temporal consistency in individual specialization over multiple foraging events. We discuss these findings broadly in the context of search images, responses to changing prey availability, and intraspecific competition pressure.

opencc-zeroOct 2023View details →

The effects of water-stress, temperature, and plant traits on the outbreak potential of a specialist and generalist spider mite species (Acari: Tetranychidae)

The host-generalist two-spotted spider mite [Tetranychus urticae (Acari: Tetranychidae); TSM] and host-specialist Banks grass mite [Oligonychus pratensis (Acari: Tetranychidae); BGM] are common pests of corn (Zea mays L.) in the arid western United States. Climate warming and decreased precipitation may promote conditions favored by these spider mites. However, rapid evolution of spider mite resistance to commercially available acaricides is driving the need for alternative solutions for managing outbreaks. Planting of drought-tolerant corn hybrids has been proposed to be a dual-purpose strategy for mitigating water deficits for irrigation and reducing leaf conditions favorable for BGM outbreaks. However, understanding of the mechanisms responsible for reducing the BGM in the field is lacking, and determining whether outbreaks of the TSM can also be averted using drought-tolerant corn is a pressing concern. We conducted a two-year field study testing a drought-tolerant corn hybrid and an analogous drought-susceptible hybrid under water-stress with artificially-infested spider mite populations. Drought-tolerant corn had larger stem diameter, more massive cobs, and greater leaf water mass compared to the drought-susceptible corn under water stress. We also found that the BGM populations were reduced on drought-tolerant plants under water-stress, as expected, but we found an opposite trend in the TSM. Lastly, water-stressed leaves were warmer, transpired less, and had higher carbon concentration, which contributed to larger investment in eggs and growth in the BGM. We anticipate that further evaluation of irrigation and crop drought-tolerance in management of agriculture systems for multiple pest species will be increasingly impactful in arid regions.

opencc-zeroFeb 2024View details →

Data from: Complex patch geometries maximize species richness at the expense of forest specialists

Habitat loss and fragmentation are the greatest threats to reptiles and amphibians (herpetofauna) around the globe, but especially in the Neotropics where high diversity and ongoing land-use change coincide. Persistence of biodiversity in fragmented systems relies both on characteristics of habitat patches, and on the permeability of the landscape that separates the patches (the 'matrix'). We sought to understand: (a) how the herpetofauna community differs between forest reserves, patches, corridors, and matrices, and (b) the landscape characteristics that increase suitability of a habitat patch. We conducted herpetofauna surveys in patches, corridors, matrices, and preserves (54 total sites) in a fragmented landscape in Costa Rica for three seasons. We recorded 1663 individuals of 52 species. We found that the herpetofauna community differed, and had lower richness and abundance, in the matrix compared to the other three habitat types. Patches and corridors supported a similar community to the forest preserves, demonstrating the conservation value of small forest remnants. Water body presence was an important predictor of richness and abundance in both patches and matrices. While total richness increased in patches with more edge, this was driven by the response of generalist species, whereas the prime indicator species of forest preserves decreased in patches with complex shapes. The differing response to landscape characteristics between specialist and generalist species demonstrates the importance of considering specific taxa when setting conservation goals, rather than using richness measures alone. Our findings can help guide preservation of forest fragments to optimize biodiversity conservation in mixed forest-pastoral landscapes.

opencc-zeroMar 2024View details →

Data from: microhabitat selection by the Oscura Mountains Colorado chipmunk (Neotamias quadrivittatus oscuraensis): an old growth pinyon-juniper woodland specialist

Habitat specialists have been largely overlooked in old growth pinyon-juniper woodlands, despite specialists exhibiting heightened sensitivity to anthropogenic habitat loss. Furthermore, small mammal relationships within pinyon-juniper woodlands have most commonly been investigated via species abundance or habitat use, rather than habitat selection, thereby providing limited management metrics. We used the Oscura Mountains Colorado chipmunk (Neotamias quadrivittatus oscuraensis) as a model organism to evaluate whether old growth conditions drive resource selection by small mammals associated with pinyon-juniper woodlands. The goal of our study was to determine resources important to the chipmunk to inform management decisions. We evaluated microhabitat selection by testing a priori predictions based on natural history characteristics of the chipmunk and the woodlands. We grouped predictions into habitat characteristics affiliated with or not affiliated with old growth. We tested predictions under a multi-stage modeling framework using generalized linear mixed models with a binomial response variable of use versus availability. Probability of selection by chipmunks increased with increasing mean juniper diameter and increasing variation of pinyon diameter and decreased with increased distance to rocky escape terrain and increased mean percent grass cover. Our findings support the classification of the Oscura Mountains Colorado chipmunk as an old growth pinyon-juniper specialist, as the chipmunk displayed disproportionate preference for old growth microhabitat conditions. We recommend management policies that conserve old growth multi-age stands of pinyons and junipers. Old growth conditions near outcroppings, escarpments, and large boulders are of particular conservation concern. Further, thinning resulting in increased grass cover may be detrimental to this old growth pinyon-juniper specialist.

opencc-zeroApr 2024View details →

Data from: Phenotypic plasticity and the effects of thermal fluctuations on specialists and generalists

Classical theories predict that relatively constant environments should generally favor specialists, while fluctuating environments should select for generalists. However, theoretical and empirical results have pointed out that generalist organisms might on the contrary perform poorly under fluctuations. In particular, if generalism is underlaid by phenotypic plasticity, performance of generalists should be modulated by the temporal characteristics of environmental fluctuations. Here, we used experiments in microcosms and a mathematical model to test whether the period or autocorrelation of thermal fluctuations mediate links between the level of generalism and the performance of organisms under fluctuations. In the experiment, thermal fluctuations consistently impeded performance compared to constant conditions. However, the intensity of this effect depended on the level of generalism: while the more specialists strains performed better under fast or negatively autocorrelated fluctuations, plastic generalists performed better under slow or positively autocorrelated fluctuations. Our model suggests that these effects of fluctuations on organisms' performance may result from a time delay in the expression of plasticity, restricting its benefits to slow-enough fluctuations. This study points out the need to further investigate the temporal dynamics of phenotypic plasticity to better predict its fitness consequences under environmental fluctuations.

opencc-by-4.0Feb 2024View details →

Root-knot nematode infection of Brassica rapa enhances the performance of a specialist root herbivore via systemically induced responses

Herbivores sharing host plants are often temporally and spatially separated, limiting direct interactions between them. Nevertheless, they can reciprocally influence each other via systemically induced plant responses, as observed in numerous study systems. In contrast, examples of such plant-mediated interactions between belowground herbivores are scarce, but we postulated that they similarly occur given the large diversity of root-interacting soil organisms. To test this hypothesis, we analyzed the performance of Delia radicum larvae feeding on main roots of Brassica rapa plants whose fine roots were infected by the root-knot nematode Meloidogyne incognita. Simultaneously, we studied the effects of M. incognita on D. radicum-induced defense responses and the accumulation of primary metabolites in the main root. We observed that almost 1.5 times as many D. radicum adults emerged from nematode-infected plants, indicating a facilitation effect of M. incognita infection. Although we observed increases in the accumulation of proteins and two essential amino-acids, the strongest effect of nematode-infection was visible in the defense response to D. radicum. We observed a 1.5 times higher accumulation of the defense-related phytohormone JA-Ile in response to D. radicum on nematode-infected plants, coinciding with a 75% increase in indole glucosinolate concentrations. Contrastingly, concentrations of aliphatic glucosinolates, secondary metabolites negatively affecting D. radicum, were 10-25% lower in nematode-infected plants. We hypothesize that the attenuated aliphatic glucosinolate concentrations result from antagonistic interactions between biosynthetic pathways of both glucosinolate classes, which was reflected in the expression of key biosynthesis genes. Our results provide explicit evidence of plant-mediated interactions between belowground organisms via systemically induced responses in roots.

opencc-zeroMay 2022View details →

Data from: Stochasticity leads to coexistence of generalists and specialists in assembling mutualistic communities

Previous models for assembling ecological networks did not include stochasticity at the level of population dynamics (e.g., demographic noise, environmental noise) and focused mainly on food webs. Here, we present a model for the assembly of mutualistic bipartite networks, such as plant-pollinator networks, and examine the influence of demographic noise on the trajectory of species and strategy diversity, i.e., the range of present strategies from specialism to generalism. We find that assembled communities show at intermediate assembly stages a maximum of species diversity and of average generalization. Our model thus provides a mechanism for non-linear, hump-shaped diversity trajectories at intermediate succession, consistent with the intermediate disturbance hypothesis. Long-term coexistence of specialists and generalists emerges only in the presence of demographic noise and is due to a persistent species turnover. These findings highlight the importance of stochasticity for maintaining long-term diversity.

opencc-zeroJun 2022View details →

Morphological measurements of two host specialists of the dipteran Tephritis conura, both in sympatry and allopatry

<div> <div> <div> <div> Adaptation to new ecological niches is known to spur population diversification and may lead to speciation if gene flow is ceased. While adaptation to the same ecological niche is expected to be parallel, it is more difficult to predict whether selection against maladaptive hybridization in secondary sympatry results in parallel divergence also in traits that are not directly related to the ecological niches. Such parallelisms in response to selection for reproductive isolation can be identified through estimating parallelism in reproductive character displacement across different zones of secondary contact. Here, we use a host shift in the phytophagous peacock fly Tephritis conura, with both host races represented in two geographically separate areas East and West of the Baltic Sea to investigate convergence in morphological adaptations. We asked i) if there are consistent morphological adaptations to a host plant shift and ii) if the response to secondary sympatry with the alternate host race is parallel across contact zones. We found surprisingly low and variable, albeit significant, divergence between host races. Only one trait, the length of the female ovipositor, which serves an important function in the interaction with the hosts, was consistently different between host races. Instead, co-existence with the other host race significantly affected the degree of morphological divergence, but the divergence was largely driven by different traits in different contact zones. Thus, local stochastic fixation or reinforcement could generate trait divergence, and additional evidence is needed to conclude whether divergence is locally adaptive. </div> </div> </div> </div>

opencc-zeroJun 2022View details →

Patch quality and habitat fragmentation shape the foraging patterns of a specialist folivore

Research on use of foraging patches has focused on why herbivores visit or quit patches, yet little is known about visits to patches over time. Food quality, as reflected by higher nutritional quality and lower plant defences, and physical patch characteristics, which offer protection from predators and weather, affect patch use and hence should influence their revisitation. Due to the potentially high costs of moving between patches, fragmented habitats are predicted to complicate foraging decisions of many animals. We aimed to determine how food quality, shelter availability and habitat fragmentation influence tree reuse by a specialist folivore, the koala, in a fragmented agricultural landscape. We GPS- tracked 23 koalas in northern New South Wales, Australia and collated number of revisits, average residence time, and average time-to-return to each tree. We measured tree characteristics including food quality (foliar nitrogen and toxic formylated phloroglucinol compounds, FPCs concentrations), tree size and tree connectedness. We also modelled the costs of locomotion between trees. Koalas re-visited isolated trees with high leaf nitrogen disproportionately often. They spent longer time in trees with high leaf nitrogen, and in large trees used for shelter. They took longer to return to trees with low leaf nitrogen. Tree connectivity reduced travel costs between patches, being either individual or groups of trees. FPC levels had no detectable effect on patch revisitation. We conclude that food quality and shelter drive koala tree re-visits. Scattered, isolated trees with nutrient-rich leaves are valuable resource patches for koalas despite movement costs to reach them.

opencc-zeroJul 2022View details →

Activity of forest specialist bats decreases towards wind turbines at forest sites

Worldwide, wind turbines are increasingly being built at forest sites to meet the goals of national climate strategies. Yet, the impact on forest ecosystems and biodiversity is barely understood. Bats may be heavily affected by wind turbines in forests, because many species depend on forest ecosystems for roosting and hunting and can experience high fatality rates at wind turbines. We performed acoustic surveys in 24 temperate forests in the low mountain ranges of Central Germany to monitor changes in the acoustic activity of bats in relation to wind turbine proximity, rotor size, vegetation structure and season. Call sequences were identified and assigned to one of three functional guilds: open-space, edge-space and narrow-space foragers, the latter being mainly forest specialists. Based on the response behaviour of bats towards wind turbines in open landscapes, we predicted decreasing bat activity towards wind turbines at forest sites, especially for narrow-space foragers. Vertical vegetation heterogeneity had a strong positive effect on all bats, yet responses to wind turbines in forests varied across foraging guilds. Activity of narrow-space foragers decreased towards turbines over distances of several hundred meters, especially towards turbines with large rotors and during midsummer months. The activity of edge-space foragers did not change with distance to turbines or season, whereas the activity of open-space foragers increased close to turbines only in late summer. Synthesis and applications: We show that narrow-space foragers avoid wind turbines in forests over a spatial scale of several hundred meters. This response was most apparent towards turbines with large rotors. Since forests are an important habitat for this guild, we advise to exclude forests with diverse vegetation structure as potential wind turbine sites and to consider compensation measures to account for habitat degradation associated with the operation of wind turbines in forests.

Figure 21 in Breeding behavior, distribution, and conservation of the Sharp-tailed Tyrant Culicivora caudacuta (Vieillot, 1818) (Aves: Tyrannidae), a South American grassland specialist

Figure 21. Records of Culicivora caudacuta. Yellow stars indicate museum specimens, dots indicate other categories of records. See Appendix 1 for details.

Figure 22 in Breeding behavior, distribution, and conservation of the Sharp-tailed Tyrant Culicivora caudacuta (Vieillot, 1818) (Aves: Tyrannidae), a South American grassland specialist

Figure 22. Culicivora caudacuta habitat occupation by Eucalyptus sp. monoculture, Araxá, Ribeirão do Inferno (07 May 2014). Photo: RSS.

Figure 1 in Breeding behavior, distribution, and conservation of the Sharp-tailed Tyrant Culicivora caudacuta (Vieillot, 1818) (Aves: Tyrannidae), a South American grassland specialist

Figure 1. Adult Sharp-tailed Tyrant Culicivora caudacuta, (11 October 2011), Patrocínio, Minas Gerais, Brazil. Photo: RSS.

Figure 20 in Breeding behavior, distribution, and conservation of the Sharp-tailed Tyrant Culicivora caudacuta (Vieillot, 1818) (Aves: Tyrannidae), a South American grassland specialist

Figure 20. Specimen of young Culicivora caudacuta at Zoologische Staatssammlung München. Photo: Markus Unsöld.

opencc-zeroMay 2024View details →

Evolution of intraspecific floral variation in a generalist-specialist pollination system

Intraspecific processes impact macroevolutionary patterns through individual variation, selection, and ecological specialisation. According to the niche variation hypothesis, the broader ecological niche of generalist species has been proposed to increase in variation among individuals, either because they are constituted of diversified specialised individuals each exploiting a fraction of the species' niche, or because they are constituted of true generalist individuals that experience relaxed selection. To test this hypothesis, we surveyed the individual floral morphology of species of Antillean Gesneriaceae, a group that has transitioned between specialisation for hummingbird pollination and generalisation multiple times throughout its evolutionary history. We characterised the profiles of corollas using geometric morphometrics and compared the intraspecific shape variance of specialists and generalists in a phylogenetic context. We used three approaches that differently accounted for the high dimensionality of morphological traits, the ancestral reconstruction of pollination syndromes over time, and the error associated with the estimation of the intraspecific variance. Our findings provide partial support for the niche variation hypothesis. If considering the whole shape in the analysis corroborated this idea, decomposing the shape into principal components indicated that not all aspects of the corolla exhibit the same pattern of variation. Specifically, pollination generalists tend to display greater intraspecific variation than specialists in terms of tubularity, but not of curvature. Accounting for the error in the estimation of the variance also reduced the support for the hypothesis, suggesting that larger sample sizes may be required to reach stronger conclusions. This study emphasises the reciprocal influence between plants and their pollinators on floral morphology at different biodiversity scales, by affecting intraspecific floral variation that can result in macroevolutionary patterns.

opencc-zeroJun 2024View details →

Utility index and vision related quality of life in patients awaiting specialist eye care

Objectives: This study aimed to ascertain utility and vision-related quality of life in patients awaiting access to specialist eye care. A secondary aim was to evaluate the association of utility indices with demographic profile and waiting time. Methods: Consecutive patients that had been waiting for ophthalmology care answered the 25-item National Eye Institute Visual Function Questionnaire (NEI VFQ-25). The questionnaire was administered when patients arrived at the clinics for their first visit. We derived a utility index (VFQ-UI) from the patients' responses, then calculated the correlation between this index and waiting time and compared utility across demographic subgroups stratified by age, sex, and care setting. Results: 536 individuals participated in the study (mean age 52.9±16.6 years; 370 women, 69% women). The median utility index was 0.85 (interquartile range [IQR] 0.70–0.92; minimum 0.40, maximum 0.97). The mean VFQ-25 score was 70.88±14.59. Utility correlated weakly and nonsignificantly with waiting time (-0.05, P = 0.24). It did not vary across age groups (P = 0.85) or care settings (P = 0.77). Utility was significantly lower for women (0.84, IQR 0.70–0.92) than men (0.87, IQR 0.73–0.93, P = 0.03), but the magnitude of this difference was small (Cohen's d = 0.13). Conclusion: Patients awaiting access to ophthalmology care had a utility index of 0.85 on a scale of 0 to 1. This measurement was not previously reported in the literature. Utility measures can provide insight into patients' perspectives and support economic health analyses and inform health policies.

Figure 1 in Notes on the jumping spider Corythalia conferta (Araneae: Salticidae), a possible myrmecophagous specialist in Argentina

Figure 1. Corythalia conferta Bayer, Höfer & Metzner. a, Left palp (male IBSI-Ara 0088), ventral view. b, Same, retrolateral view. c, Same, prolateral view. d, Copulatory bulb (male IBSI-Ara 0277), cleared ventral view. e, Chelicerae (male IBSI-Ara 1326), anterior view. f, Tibia of palp (IBSI-Ara 0277), prolateral view. g, Female (IBSI-Ara 0045) cleared epigyne, ventral view. All measurements in mm.

Figure 7 in Notes on the jumping spider Corythalia conferta (Araneae: Salticidae), a possible myrmecophagous specialist in Argentina

Figure 7. Jumping spiders Corythalia conferta in nature preying on different ants. a,c, Atta Fabricius. b,d, Indeterminate ants. e,i, Camponotus (Mayr) sp1. f, Mix of Cephalotes Latreille and Pseudomyrmex Lund sp2. g, Pseudomyrmex sp2. h, Camponotus sp3.

Figure 4 in Notes on the jumping spider Corythalia conferta (Araneae: Salticidae), a possible myrmecophagous specialist in Argentina

Figure 4. Hypothetical phylogeny of nine Corythalia species based on the neighbor-joining method for analysis of molecular data (barcode sequences).

Figure 6 in Notes on the jumping spider Corythalia conferta (Araneae: Salticidae), a possible myrmecophagous specialist in Argentina

Figure 6. Pie chart depicting proportion of each type of of prey ant captured and consumed by Corythalia conferta in this study. The "Leaf-cutting ants" are represented by ants of the genera Atta Fabricius and Acromyrmex Mayr.