Burrow builders as ecosystem engineers for pit-building antlions (Neuroptera: Myrmeleontidae).

Burrow builders are often classified as ecosystem engineers because their digging activities regulate the availability of resources for other organisms. As antlion larvae prefer to construct their traps in bare sandy or loose soil, they could benefit from burrowing activities. We investigated the role of burrow builders as ecosystem engineers for antlions (Myrmeleontidae) in a tropical semideciduous forest in Mexico. The number of traps of antlion larvae was recorded on 30 sampling quadrats (45 cm) at the entrance of burrows (of unidentified builders) and on 30 paired off-burrow quadrats. Additionally, the percentage of bare soil was estimated for the 60 quadrats sampled. Of the 30 quadrats at the entrance of burrows, a total of 336 traps were recorded, with 21 (70%) of them having at least one trap, while for the 30 off-burrows quadrats, only two (6.6%) of them had traps, just three in total. The percentage of bare soil and the abundance of traps were significantly greater in quadrats at the entrance of burrows compared to quadrats without burrows. The abundance of traps at the entrance of burrows was positively affected by the percentage of bare soil. The few traps in the off-burrows quadrats suggested that, in addition to the limited bare soil, ground compactness probably limits the establishment of antlion larvae. Otherwise, when digging, burrow builders create small patches of bare sandy soils that are used by these insects. We concluded that the ecosystem engineering effect of burrow builders is an important structuring element for antlion populations in the tropical semideciduous forest studied.

Ecosystem engineering by leaf-rolling mites enhances arthropod diversity.

Many arthropods modify parts of plants through the construction of domiciles or by consuming plant tissues that, after abandoned, can be used as shelter by other arthropods in a facilitating interaction process. We examined, for the first time, the potential of leaf-rolling mites to indirectly influence arthropod communities in natural forests by providing shelter sites. In early June 2019, we found a high density of leaves of Amphitecna tuxtlensis (Bignoniaceae) rolled by an undetermined leaf-rolling mite species in a tropical rainforest, in Mexico. We tested whether the species richness, abundance, and colonization frequency of arthropods was greater in rolled compared with expanded leaves. We collected 5 rolled leaves and 5 fully expanded leaves from 15 A. tuxtlensis trees (N = 150 sampled leaves) and recorded all arthropods on each leaf. We recorded 1421 arthropods from 67 unique morphospecies. We found 39 individuals from 23 morphospecies of arthropods in expanded leaves, and 1382 individuals from 56 morphospecies in rolled leaves. Ants were the most abundant and frequent group and utilized the rolled leaves mainly as nesting sites; 1260 ant individuals were found in 30 nests from three species. Arthropod species richness, abundance, and colonization frequency were greater in rolled leaves compared with expanded leaves. We concluded that the ecosystem engineering effect of leaf-rolling mites may be an important structuring element for arthropod communities on plants through an increase of high quality food resources and shelter sites for other arthropods, as well as nesting sites for ants.

Feeding Specialization of Flies (Diptera: Richardiidae) in Aroid Infructescences (Araceae) of the Neotropics.

Evolution and radiation between insects and flowering plants are both opportunistic and obligatory when the former feeds on the reproductive structures of the latter, whereas direct and indirect effects can influence the fitness of individuals, populations, and plant communities. The Araceae family constitutes an important element of the tropical rainforest of the Neotropics, and its morphology and floral biology provide a remarkable system for studying trophic interactions with insects, including the Richardiidae flies (Diptera). We studied the trophic interactions of the aroid-fly system, assessing infestation rates under natural conditions over an annual cycle. In the Neotropical region, we discovered for the first time that seven aroid species became infested by four richardiid species: Beebeomyia tuxtlaensis Hernández-Ortiz and Aguirre with Dieffenbachia oerstedii Schott and D. wendlandii Schott; B. palposa (Cresson) with Xanthosoma robustum Schott; Beebeomyia sp.3. in association with Philodendron radiatum Schott, P. tripartitum (Jacq.) Schott, and P. sagittifolium Liebm.; while Sepsisoma sp. only infested Rhodospatha wendlandii Schott. Infestation rates differed significantly among hosts, but comparisons with morphological traits did not provide evidence of a causal factor of the infestation. In contrast, larval density and time of development both exhibited significant differences between hosts. The findings suggest the high specialization of the flies, and that intrinsic factors of the plants, such as the presence of secondary metabolites and their maturation periods, may influence their infestation rates.

Effects of Florivory on Floral Visitors and Reproductive Success of Sagittaria lancifolia (Alismataceae) in a Mexican Wetland.

Florivores consume floral structures with negative effects on plant fitness and pollinator attraction. Several studies have evaluated these consequences in hermaphroditic plants, but little is known about the effects on monoecious and dioecious species. We characterize the florivory and its effects on floral visitors and reproductive success in a monoecious population of Sagittaria lancifolia. Five categories of florivory were established according to the petal area consumed. Visits were recorded in male and female flowers within the different damage categories. Reproductive success was evaluated through fruit number and weight, as well as the number of seeds per fruit. Our results show that the weevil Tanysphyrus lemnae is the main florivore, and it mainly damages the female flowers. Hymenoptera were recorded as the most frequent visitors of both male and female flowers. Male and female flowers showed differences in visit frequency, which decreases as flower damage increases. Reproductive success was negatively related to the level of damage. We found that florivory is common in the population of S. lancifolia, which can exert a strong selective pressure by making the flowers less attractive and reducing the number of seeds per fruit. Future studies are needed to know how florivores affect plant male fitness.

Buzz-Pollination in a Tropical Montane Cloud Forest: Compositional Similarity and Plant-Pollinator Interactions.

Buzz-pollinated plants are an essential source of pollen for a significant portion of local bee communities. Buzz pollination research has focused on studying the properties of bee buzzes and their implications on pollen release, morphological specialization of flowers, and the reproductive ecology of buzz-pollinated plants. In contrast, diversity patterns and ecological interactions between bees and buzz-pollinated plants have been studied less. This study analyzed the buzzing bee community of twelve tropical buzz-pollinated co-occurring plant species in a tropical montane cloud forest during the flowering periods of two consecutive years, focusing on diversity, compositional similarity, structure, and specialization (H2´) of the network. Twenty-one bee species belonging to Apidae, Colletidae, and Halictidae were recorded, fifteen species in 2014, and eighteen in 2015. Floral display and visited flowers doubled from first to second year, although the flowering period was 2 months longer in the first year. Bee compositional similarity between plants tended to be low; however, this was due rather to a high nestedness than species replacement. Temporal bee compositional similarity was also low but variable, and different plant species showed the highest similarity between years. The number of bee visits depended significantly on the number of flowers and years. Interactions between bees and plants showed a tendency to generalization. Compared to other buzz-pollinated networks, specialization (H2´) was similar, but diversity was low and the network small. In endangered ecosystems like the Mexican cloud forest, however, buzzing bees support biodiversity and provide an essential ecological service by pollinating dominant understory flora.

Vertical and Horizontal Trophic Networks in the Aroid-Infesting Insect Community of Los Tuxtlas Biosphere Reserve, Mexico.

Insect-aroid interaction studies have focused largely on pollination systems; however, few report trophic interactions with other herbivores. This study features the endophagous insect community in reproductive aroid structures of a tropical rainforest of Mexico, and the shifting that occurs along an altitudinal gradient and among different hosts. In three sites of the Los Tuxtlas Biosphere Reserve in Mexico, we surveyed eight aroid species over a yearly cycle. The insects found were reared in the laboratory, quantified and identified. Data were analyzed through species interaction networks. We recorded 34 endophagous species from 21 families belonging to four insect orders. The community was highly specialized at both network and species levels. Along the altitudinal gradient, there was a reduction in richness and a high turnover of species, while the assemblage among hosts was also highly specific, with different dominant species. Our findings suggest that intrinsic plant factors could influence their occupation, and that the coexistence of distinct insect species in the assemblage could exert a direct or indirect influence on their ability to colonize such resources.

Flower-mediated plant-butterfly interactions in an heterogeneous tropical coastal ecosystem.

BACKGROUND: Interspecific interactions play an important role in determining species richness and persistence in a given locality. However at some sites, the studies, especially for interaction networks on adult butterflies are scarce. The present study aimed the following objectives: (1) determine butterfly species richness and diversity that visit flowering plants, (2) compare species richness and diversity in butterfly-plant interactions among six different vegetation types and (3) analyze the structure of butterfly-flowering plant interaction networks mediated by flowers. METHODS: The study was developed in six vegetation types within the natural reserve of La Mancha, located in Veracruz, Mexico. In each vegetation type, we recorded the frequency of flower visits by butterflies monthly in round plots (of radius 5 m) for 12 months. We calculated Shannon diversity for butterfly species and diversity of interactions per vegetation type. We determined the classic Jaccard similarity index among vegetation types and estimated parameters at network and species-level. RESULTS: We found 123 species of butterflies belonging to 11 families and 87 genera. The highest number of species belonged to Hesperiidae (46 species), followed by Nymphalidae (28) and Pieridae (14). The highest butterfly diversity and interaction diversity was observed in pioneer dune vegetation (PDV), coastal dune scrub (CDS) and tropical deciduous flooding forest and wetland (TDF-W). The same order of vegetation types was found for interaction diversity. Highest species similarity was found between PDV-CDS and PDV-TDF. The butterfly-plant interaction network showed a nested structure with one module. The species Ascia monuste, Euptoieta hegesia and Leptotes cassius were the most generalist in the network, while Horama oedippus, E. hegesia, and L. cassius were the species with highest dependencies per plant species. DISCUSSION: Our study is important because it constitutes a pioneer study of butterfly-plant interactions in this protected area, at least for adult butterflies; it shows the diversity of interactions among flowering plants and butterflies. Our research constitutes the first approach (at a community level) to explore the functional role of pollination services that butterflies provide to plant communities. We highlighted that open areas show a higher diversity and these areas shared a higher number of species that shaded sites. In the interaction networks parameters, our results highlighted the higher dependence of butterflies by the flowers on which they feed than vice versa. In conclusion, the plant species (as a feeding resource) seem to limit the presence of butterfly species. Thus, this protected area is highly relevant for Lepidoptera diversity and the interaction between these insects and flowering plants. We suggest that studying plant and butterfly diversity in tropical habitats will provide insight into their interspecific interactions and community structure.