Multidimensional niche differentiation and morphological adaptations between two sympatric caterpillars of Papilio (Lepidoptera: Papilionidae)

Competitive intransitivity is mostly considered outside the main body of coexistence theories that rely primarily on the role of niche overlap and differentiation. How the interplay of competitive intransitivity and niche overlap jointly affects species coexistence has received little attention. Here, we consider a rock–paper–scissors competition system where interactions between species can represent the full spectra of transitive–intransitive continuum and niche overlap/differentiation under different levels of competition asymmetry. By comparing results from pair approximation that only considers interference competition between neighbouring cells in spatial lattices, with those under the mean‐field assumption, we show that 1) species coexistence under transitive competition is only possible at high niche differentiation; 2) in communities with partial or pure intransitive interactions, high levels of niche overlap are not necessary to beget species extinction; and 3) strong spatial clustering can widen the condition for intransitive loops to facilitate species coexistence. The two mechanisms, competitive intransitivity and niche differentiation, can support species persistence and coexistence, either separately or in combination. Finally, the contribution of intransitive loops to species coexistence can be enhanced by strong local spatial correlations, modulated and maximised by moderate competition asymmetry. Our study, therefore, provides a bridge to link intransitive competition to other generic ecological theories of species coexistence.

The maintenance of sex is difficult to explain in the face of the demographic advantages of asexuality, especially when sexual and asexual lineages co-occur and compete. Here, we test if niche divergence and host plant specialization can contribute to the maintenance of sympatric populations of two closely related, sexual and asexual Aptinothrips grass thrips species. In mesocosm experiments, ecological niche and host plant specialization were inferred from thrips performances on different grass species used as hosts in natural populations. Sexual and asexual thrips performed best on different grass species, indicating niche differentiation. The asexual species was also characterized by a broader ecological niche than the sexual one. However, niche differentiation is unlikely to explain the maintenance of the two species in sympatry, because the reproductive rate of asexual females generally exceeded that of sexual ones. Surprisingly, the asexual but not sexual species showed geographic variation in the ecological niche. This geographic variation likely stems from variation in clonal assemblages among locations because different asexual genotypes have different ecological niches. Across natural populations, the performance of asexual females on a specific grass species was furthermore positively correlated with the abundance of that grass species, consistent with adaptation to locally abundant grasses. Altogether, our results suggest that niche differentiation contributes little to the co-occurrence of sexual and asexual grass thrips and that asexuality facilitates adaptation to a diversity of co-occurring host plants.

A large proportion of phytophagous insect species are specialised on one or a few host plants, and female host plant preference is predicted to be tightly linked to high larval survival and performance on the preferred plant(s). Specialisation is likely favoured by selection under stable circumstances, since different host plant species are likely to differ in suitability-a pattern usually explained by the "trade-off hypothesis", which posits that increased performance on a given plant comes at a cost of decreased performance on other plants. Host plant specialisation is also ascribed an important role in host shift speciation, where different incipient species specialise on different host plants. Hence, it is important to determine the role of host plants when studying species divergence and niche partitioning between closely related species, such as the butterfly species pair Leptidea sinapis and Leptidea reali. In Sweden, Leptidea sinapis is a habitat generalist, appearing in both forests and meadows, whereas Leptidea reali is specialised on meadows. Here, we study the female preference and larval survival and performance in terms of growth rate, pupal weight and development time on the seven most-utilised host plants. Both species showed similar host plant rank orders, and larvae survived and performed equally well on most plants with the exceptions of two rarely utilised forest plants. We therefore conclude that differences in preference or performance on plants from the two habitats do not drive, or maintain, niche separation, and we argue that the results of this study do not support the trade-off hypothesis for host plant specialisation, since the host plant generalist Leptidea sinapis survived and performed as well on the most preferred meadow host plant Lathyrus pratensis as did Leptidea reali although the generalist species also includes other plants in its host range.

Understanding the factors that allow the coexistence of multiple species in biological communities is a central question in ecology, and various mechanisms have been proposed to explain the maintenance of this diversity. One mechanism is niche partitioning, which predicts that, to avoid interspecific competition, species must differentiate in resource use to coexist. Therefore, in this study, we analyzed the three main niche dimensions (temporal, spatial, and trophic) of six Ectatomma ant species (E. permagnum, E. opaciventre, E. edentatum, E. planidens, E. tuberculatum, and E. brunneum) to understand the importance of resource partitioning for their coexistence, as phylogenetically related species (like those of the same genus) have more similar niche spaces, resulting in strong competition when these are overlapped. To investigate spatial variation, sampling was carried out in three vegetation types of the Cerrado (open savanna, dense savanna, and dry forest) using pitfall traps. To determine the temporal niche, pitfall traps were used in a way that they remained active for a 2-hour period: in the morning (06:00 - 08:00 am), in the afternoon (12:00 -14:00 pm), and in the evening (19:00- 21:00 pm). Additionally, to evaluate if the foraging period correlates with species' critical thermal limits (CTmax and CTmin), thermal tolerance was determined using a dry bath equipment. Finally, the trophic niche was determined through isotopic signature (δ 15N) using stable isotope analysis. The results of this study indicate habitat preference for all species except E. edentatum, which occurred at similar frequency in all sampled physiognomies. Regarding foraging periods, none of the species were found foraging exclusively during a single sampling period, with most being active at various times of the day. However, species with lower heat tolerance avoided foraging during the hottest times of the day, while species with higher thermal limits were most active during periods with higher temperatures. Additionally, we found high overlap in trophic positions, except for E. tuberculatum. Thus, although most Ectatomma species occupy the same trophic position, the overlap in the food niche appears to be mitigated by certain complementarities in other niche dimensions, which may help promote the coexistence of these species in the Cerrado. Therefore, this study reinforces the hypothesis of niche partitioning as a mechanism for the coexistence of ant species and provides valuable information about the natural history of the genus Ectatomma.

Niche partitioning is a widespread ecological strategy within trophic guilds, ensuring the coexistence of sympatric species by reducing interspecific competition. Stable isotope analysis of carbon and nitrogen and isotopic niche metrics (width and overlap) are used as a proxy to investigate niche partitioning among species of a guild. In our study, we investigated if niche partitioning was an ecological mechanism contributing to the coexistence of granivorous birds from the same geographic region along time, employing an isotopic approach. We sampled and isotopically analyzed (δ13C and δ15N values) wing feathers from 58 specimens of granivorous birds collected between 1900 and 1966 in southeastern Brazil. We grouped birds according to the main habitat type used by them (forest: Cyanoloxia brissonii, Leptotila rufaxilla, and Leptotila verreauxi; and grassland: Columbina squammata and Sicalis flaveola). We used the Isotopic Richness (IRic) metric to measure the isotopic niche width and the Isotopic Similarity (ISim) and Isotopic Nestedness (INes) metrics to measure the niche overlap between groups and species. The results of low isotopic niche overlap suggest that common granivorous birds had a clear niche partitioning in southeastern Brazil in the late past, especially through foraging in distinct habitat types (forest and grassland; ISim ​= ​0.1, INes ​= ​0.2). Niche overlaps in almost all species-by-species comparisons were low (ISim ≤0.3, INes ≤0.4), except between C. brissonii and L. verreauxi (ISim ​= ​0.6, INes ​= ​1.0). These results suggest that these birds, belonging to the same trophic guild, coexisted through niche and resource partitioning. Despite being considered a plastic trophic guild, the isotopic niche partitioning among granivorous birds indicates that each of these species uses a set of specific resources and habitats. This raises an ecological concern about the homogenization of landscapes across the Neotropics, oversimplifying food resources and habitats to granivorous birds.

Carnivores play key roles in maintaining ecosystem structure and function as well as ecological processes, understanding how sympatric species coexistence mechanism in natural ecosystems is a central research topic in community ecology and biodiversity conservation. In this study, we explored intra- and interspecific niche partitioning along spatial, temporal, and dietary niche partitioning between apex carnivores (wolf Canis lupus, snow leopard Panthera uncia, Eurasian lynx Lynx lynx) and mesocarnivores (Pallas’s cat Otocolobus manul, red fox Vulpes vulpes, Tibetan fox Vulpes ferrilata) in the Qilian Mountain national park of China using camera trapping data and DNA metabarcoding sequencing data. Our study showed that apex carnivore species had more overlap temporally (the value of time overlap from 0.661 to 0.900) or trophically (the value of diet overlap from 0.458 to 0.892), mesocarnivore species had high dietary overlap with each other (the value of diet overlap from 0.945 to 0.997), and apex carnivore and mesocarnivore species had high temporal overlap (the value of time overlap from 0.497 to 0.855). Large dietary overlap was observed between wolf and snow leopard (Pianka’s index=0.892) and Pallas’s cat and Tibetan fox (Pianka’s index=0.997) and suggesting increased resource competition for these pair species were existed. We conclude that spatial niche partitioning playing a key role in facilitating the coexistence of apex carnivore species, spatial and temporal niche partitioning facilitate the coexistence of mesocarnivore species, and spatial and dietary niche partitioning facilitate the coexistence between apex and mesocarnivore species. Our findings address, for the first time, niche partitioning was considered across temporal, spatial and dietary dimensions and diverse coexistence patterns of carnivore species were presented in the Qilian Mountain national park of China. These finding will contribute substantially to current understanding of carnivore guilds and effective conservation management in fragile alpine ecosystems.

Bollworm, Heliothis zea (Boddie), and tobacco budworm, H. virescens (F.) larvae were collected at weekly intervals from 6 April through 28 August 1981 from several species of wild and cultivated host plants in the delta of Mississippi. The species, seasonal occurrence, and abundance of Heliothis larvae and their larval parasites in each species of host plant were determined. Four species of parasites, Microplitts croceipes (Cresson), Cotesia (= Apanteles) marginiventris (Cresson), Cardiochiles nigriceps Vierick, and Campoletis sonorensis (Cameron) were reared from Heliothis larvae. The highest and lowest numbers of species of parasites and percentage of parasitism of Heliothis larvae occurred in species of early season wild host plants. M. croceipes parasitized larger numbers of Heliothis spp. larvae in more species of host plants and was active over a longer period than any other parasite species. The decline in the incidence of parasitism of Heliothis in cotton, Gossypium hirsutum L., and soybeans, Glycine max (L.) Merr., during mid- and late season may have resulted from the rapid and vast expansion in host plant habitat and from applications of insecticides.

1. In nature various mechanisms that provide some refuges for inferior species to escape from competition act together to promote the species coexistence in a local community. We propose a method to evaluate simultaneously the relative importance of different mechanisms for the species coexistence, focusing on a mycophagous drosophilid community depending on a multispecies fungal host system, where two mechanisms – aggregation over patches of single fungal species and resource partitioning at the fungal species level – can act together. The data are based on the numbers of adult insects emerging from naturally occurring fungi collected from a temperate forest in northern Japan.2.We confirm the finding ofSevenster & van Alphen (1996)that large patches are low‐density refuges despite the large absolute numbers of competitors on them, and therefore adopt new measures for intra‐ and interspecific aggregations and the species‐persistence criterion, which were developed bySevenster (1996)to take account of variable patch sizes in calculating the aggregation measures.3.The calculated measures are compared among three analyses for fungal resources: AR‐analysis (the original data‐set from multispecies fungal patches) in which both aggregation and resource partitioning can act together; R‐analysis (combining the data for all patches of each fungal species) in which only resource partitioning at the fungal species level can act; and A‐analysis (calculating the measures independently for each fungal species) in which only aggregation process can act as a coexistence mechanism.4.Intraspecific aggregation over multispecies fungal patches is strengthened by both aggregation and resource partitioning processes.5.We reconfirm the finding ofSevenster & van Alphen (1996)that interspecific associations are consistent over years, and support their claim that such consistent associations should be taken as real aspects of the community structure.6.Measures for the persistence criterion (T), the ‘relative effect of competitor aggregation’, are less than unity, satisfying the necessary and sufficient condition for the species persistence, in most drosophilid species concerned; these tend to be smaller in AR‐analysis than in R‐ or A‐analysis, suggesting facilitation of the species coexistence by both aggregation and resource partitioning in the mycophagous drosophilid community studied.7.Differences inT‐value between AR‐ and R‐analyses and between AR‐ and A‐analyses may indicate relative contributions of aggregation and resource partitioning, respectively, to the species coexistence. We propose a method to compare various communities in a multi‐dimensional space with regard to the relative importance of different coexistence mechanisms.

Carnivores play key roles in maintaining ecosystem structure and function as well as ecological processes. Understanding how sympatric species coexist in natural ecosystems is a central research topic in community ecology and biodiversity conservation. In this study, we explored intra- and interspecific niche partitioning along spatial, temporal, and dietary niche partitioning between apex carnivores (wolf Canis lupus, snow leopard Panthera uncia, Eurasian lynx Lynx lynx) and mesocarnivores (Pallas's cat Otocolobus manul, red fox Vulpes vulpes, Tibetan fox Vulpes ferrilata) in Qilian Mountain National Park, China, using camera trapping data and DNA metabarcoding sequencing data. Our study showed that apex carnivore species had more overlap temporally (coefficients of interspecific overlap ranging from 0.661 to 0.900) or trophically (Pianka's index ranging from 0.458 to 0.892), mesocarnivore species had high dietary overlap with each other (Pianka's index ranging from 0.945 to 0.997), and apex carnivore and mesocarnivore species had high temporal overlap (coefficients of interspecific overlap ranging from 0.497 to 0.855). Large dietary overlap was observed between wolf and snow leopard (Pianka's index = 0.892) and Pallas's cat and Tibetan fox (Pianka's index = 0.997), suggesting the potential for increased resource competition for these species pairs. We concluded that spatial niche partitioning is likely to key driver in facilitating the coexistence of apex carnivore species, while spatial and temporal niche partitioning likely facilitate the coexistence of mesocarnivore species, and spatial and dietary niche partitioning facilitate the coexistence between apex and mesocarnivore species. Our findings consider partitioning across temporal, spatial, and dietary dimensions while examining diverse coexistence patterns of carnivore species in Qilian Mountain National Park, China. These findings will contribute substantially to current understanding of carnivore guilds and effective conservation management in fragile alpine ecosystems.

Carnivores play key roles in maintaining ecosystem structure and function as well as ecological processes. Understanding how sympatric species coexist in natural ecosystems is a central research topic in community ecology and biodiversity conservation. In this study, we explored intra- and interspecific niche partitioning along spatial, temporal, and dietary niche partitioning between apex carnivores (wolf Canis lupus, snow leopard Panthera uncia, Eurasian lynx Lynx lynx) and mesocarnivores (Pallas’s cat Otocolobus manul, red fox Vulpes vulpes, Tibetan fox Vulpes ferrilata) in Qilian Mountain National Park, China, using camera trapping data and DNA metabarcoding sequencing data. Our study showed that apex carnivore species had more overlap temporally (coefficients of interspecific overlap ranging from 0.661 to 0.900) or trophically (Pianka’s index ranging from 0.458 to 0.892), mesocarnivore species had high dietary overlap with each other (Pianka’s index ranging from 0.945 to 0.997), and apex carnivore and mesocarnivore species had high temporal overlap (coefficients of interspecific overlap ranging from 0.497 to 0.855). Large dietary overlap was observed between wolf and snow leopard (Pianka’s index = 0.892) and Pallas’s cat and Tibetan fox (Pianka’s index = 0.997), suggesting the potential for increased resource competition for these species pairs. We concluded that spatial niche partitioning is likely to key driver in facilitating the coexistence of apex carnivore species, while spatial and temporal niche partitioning likely facilitate the coexistence of mesocarnivore species, and spatial and dietary niche partitioning facilitate the coexistence between apex and mesocarnivore species. Our findings consider partitioning across temporal, spatial, and dietary dimensions while examining diverse coexistence patterns of carnivore species in Qilian Mountain National Park, China. These findings will contribute substantially to current understanding of carnivore guilds and effective conservation management in fragile alpine ecosystems.

Carnivores play key roles in maintaining ecosystem structure and function as well as ecological processes. Understanding how sympatric species coexist in natural ecosystems is a central research topic in community ecology and biodiversity conservation. In this study, we explored intra- and interspecific niche partitioning along spatial, temporal, and dietary niche partitioning between apex carnivores (wolf Canis lupus, snow leopard Panthera uncia, Eurasian lynx Lynx lynx) and mesocarnivores (Pallas’s cat Otocolobus manul, red fox Vulpes vulpes, Tibetan fox Vulpes ferrilata) in Qilian Mountain National Park, China using camera trapping data and DNA metabarcoding sequencing data. Our study showed that apex carnivore species had more overlap temporally (coefficients of interspecific overlap ranging from 0.661 to 0.900) or trophically (Pianka’s index ranging from 0.458 to 0.892), mesocarnivore species had high dietary overlap with each other (Pianka’s index ranging from 0.945 to 0.997), and apex carnivore and mesocarnivore species had high temporal overlap (coefficients of interspecific overlap ranging from 0.497 to 0.855). Large dietary overlap was observed between wolf and snow leopard (Pianka’s index=0.892) and Pallas’s cat and Tibetan fox (Pianka’s index=0.997), suggesting the potential for increased resource competition for these species pairs. We concluded that spatial niche partitioning is likely to key driver in facilitating the coexistence of apex carnivore species, while spatial and temporal niche partitioning likely facilitate the coexistence of mesocarnivore species, and spatial and dietary niche partitioning facilitate the coexistence between apex and mesocarnivore species. Our findings consider partitioning across temporal, spatial and dietary dimensions while examining diverse coexistence patterns of carnivore species in Qilian Mountain National Park, China. These findings will contribute substantially to current understanding of carnivore guilds and effective conservation management in fragile alpine ecosystems.

Carnivores play key roles in maintaining ecosystem structure and function as well as ecological processes. Understanding how sympatric species coexist in natural ecosystems is a central research topic in community ecology and biodiversity conservation. In this study, we explored intra- and interspecific niche partitioning along spatial, temporal, and dietary niche partitioning between apex carnivores (wolf Canis lupus, snow leopard Panthera uncia, Eurasian lynx Lynx lynx) and mesocarnivores (Pallas’s cat Otocolobus manul, red fox Vulpes vulpes, Tibetan fox Vulpes ferrilata) in Qilian Mountain National Park, China, using camera trapping data and DNA metabarcoding sequencing data. Our study showed that apex carnivore species had more overlap temporally (coefficients of interspecific overlap ranging from 0.661 to 0.900) or trophically (Pianka’s index ranging from 0.458 to 0.892), mesocarnivore species had high dietary overlap with each other (Pianka’s index ranging from 0.945 to 0.997), and apex carnivore and mesocarnivore species had high temporal overlap (coefficients of interspecific overlap ranging from 0.497 to 0.855). Large dietary overlap was observed between wolf and snow leopard (Pianka’s index = 0.892) and Pallas’s cat and Tibetan fox (Pianka’s index = 0.997), suggesting the potential for increased resource competition for these species pairs. We concluded that spatial niche partitioning is likely to key driver in facilitating the coexistence of apex carnivore species, while spatial and temporal niche partitioning likely facilitate the coexistence of mesocarnivore species, and spatial and dietary niche partitioning facilitate the coexistence between apex and mesocarnivore species. Our findings consider partitioning across temporal, spatial, and dietary dimensions while examining diverse coexistence patterns of carnivore species in Qilian Mountain National Park, China. These findings will contribute substantially to current understanding of carnivore guilds and effective conservation management in fragile alpine ecosystems.

The degree of adaptation of herbivorous insects to their local flora is an important component of the evolutionary processes that lead to host plant specialization in insects. In this study we investigated geographic variations in the oviposition preference of the leaf beetleOreina elongataSuffrian (Coleoptera: Chrysomelidae: Chrysolini) in relation to differences in host plant specialization, in the field. We focused on the mechanisms of host choice and asked whether potential differences among populations are due to variations in host plant ranking and/or host plant specificity. We performed a combination of simultaneous choice and sequential no‐choice experiments with two of the major host plants of the beetle [Cirsium spinosissimum(L.) andAdenostyles alliariae(Gouan) (Asteraceae)]. The results suggested that spatial variation in host plant specialization has resulted in differences between populations in some aspects of the oviposition choice ofO. elongata, while other aspects seem unaffected. We found no variation in host plant ranking among populations, as estimated in simultaneous choice tests. In contrast, the sequential no‐choice test indicated that host plant specificity was lower in a population that never encountered the highest ranked plant in the field. This finding agreed with our expectations, and we discuss our results in relation to the commonly used hierarchical threshold model. The results suggested that the mechanism for the differences in specificity is the variation among populations in the general motivation to oviposit, rather than quantitative differences in relative preference for the two hosts. We stress that it is essential to establish which of the two mechanisms is most important, as it will affect the probability of evolutionary change in host plant ranking.

Two new species of the genus Asterina are described from living leaves collected in provinces Chiriquí and Bocas del Toro in western Panama. Asterina alloplecti on Alloplectus ichtyoderma (Gesneriaceae) differs from other Asterina on Gesneriaceae by its stalked appressoria and host relationship. Asterina compsoneurae on Compsoneura sprucei (Myristicaceae) can be distinguished from other members of Asterina on Myristicaceae by its larger ascomata, larger, prominently spinose ascospores and host relationship. New records for Panama are Asterina corallopoda from a new host plant species (Solanum trizygum, Solanaceae), A. diplopoda, A. ekmanii from a new host plant species (Gonzalagunia rudis, Rubiaceae), A. siphocampyli from a new host plant genus and species (Burmeistera vulgaris, Campanulaceae) and A. styracina from a new host-plant species (Styrax argenteus, Styracaceae). This study increases the number of species of Asterina known for Panama from 12 to 19 and the number of Asterinaceae from 14 to 21. Asterina corallopoda, A. diplopoda, A. ekmanii, A. siphocampyli and A. styracina are illustrated for the first time. A phylogeny inferred from the analysis of LSU rDNA sequences of species of Asterina is presented. The diversity and host-plant patterns of known Neotropical species of Asterina are discussed.

<p>Ecological interactions can play a major role in driving the process of speciation when they lead to a decrease in gene flow between diverging lineages. Various pre- and post-zygotic ecological barriers to gene flow are known to be important in speciation, but the specific barriers that cause the initiation of speciation are often unknown. Phytophagous (plant feeding) insects are powerful systems for evaluating ecologically based reproductive barriers because these organisms generally have a history of traits such as host shifting and host mediated sexual selection associated with speciation. Previous work on the sunflower maggot fly (Strauzia longipennis) indicates that three genetically distinct, diverging varieties co-occur on the host plant Helianthus tuberosus. In this work, I 1) confirm the existence of three diverging varieties by genotyping microsatellite loci, 2) evaluate the presence and strength of three pre-zygotic barriers to reproduction - habitat isolation, pre-mating sexual isolation, and allochronic isolation - between the varieties, and 3) measure the impacts of allochronic isolation on resource partitioning by evaluating host preference, oviposition location, and larval location between diverging Strauzia varieties sharing the same host plant species. I find evidence of pre-mating sexual isolation and allochronic isolation between the three varieties, indicating that these may be reproductive barriers that arise during early stages of divergence. These barriers may have occurred without (or before) the host-shift that is typical of many other diverging phytophagous insect systems. I also find evidence that allochronic isolation leads to resource partitioning of the single host plant resource, which may help the three varieties share the same host plant.</p>