Tolerance Mitigates Gall Effects When Susceptible Plants Fail to Elicit Induced Defense.

Variations in plant genotypes and phenotypes are expressed in ways that lead to the development of defensive abilities against herbivory. Induced defenses are mechanisms that affect herbivore insect preferences and performance. We evaluated the performance of resistant and susceptible phenotypes of Bauhinia brevipes (Fabaceae) against attacks by the gall-inducing insect Schizomyia macrocapillata (Diptera). We hypothesized that there is a positive relationship between resistance to S. macrocapillata and host plant performance because resistance can have a high adaptive value. We evaluated plant architecture, nutritional leaf quality, leaf fluctuating asymmetry, and reproductive capacity between phenotypes. Plant performance was evaluated at three ontogenetic stages: seed, seedling, and juvenile. Overall, there were no differences in vegetative and reproductive performance or asymmetry between the resistant and susceptible mature plants. We found no relationship between leaf nutritional quality and resistance to S. macrocapillata. Plant performance was consistent across ontogeny for both phenotypes, except for five variables. Contrary to our expectations, the susceptible plants performed equally well or better than the resistant plants, suggesting that tolerance and overcompensation to herbivory in B. brevipes may be mediated by induced defense. Our study highlights the importance of multiple layers of plant defense against herbivory, where plant tolerance acts as a secondary barrier in plants susceptible to gall-inducing insects.

Patterns in Wing Morphology and Fluctuating Asymmetry in Eulaema nigrita along an Altitudinal Gradient in the Brazilian Rupestrian Grassland.

Mountain ecosystems experience abrupt abiotic changes that represent environmental filters for many organisms, shaping their phenotypic expressions. However, little is known about the morphological and symmetric adjustments of native bees along altitudinal gradients. We evaluated the changes on wing morphology, wing size, and vein fluctuating asymmetry (FA) of Eulaema nigrita Lepeletier (Apidae: Euglossini) associated with climatic variables along an altitudinal gradient in the rupestrian grassland (known also as campo rupestre or rupestrian field) of Serra do Cipó, Brazil. Seven sampling points along the altitudinal gradient were selected and distributed among 800 and 1400 m.a.s.l., and then, 40 individuals of E. nigrita were collected per each altitudinal point to determine the FA levels and the morphological changes using geometric morphometric techniques. We found that the wing size of E. nigrita decreased with increasing altitude. At the highest altitudes, the levels of FA of the wing veins were greater compared to bees from lower altitudes. We detected significant changes in wing morphology along the altitudinal gradient; bees of lower altitudes showed longer and wider wings than bees of higher altitudes, which had narrower and less elongated wings. Our results show a set of morphological adjustments and phenotypic expressions in E. nigrita associated with the variation in environmental conditions along the altitudinal gradient. We highlight the importance of environmental variables as insect-stressor factors, and that FA and geometric morphometric can be excellent tools for monitoring and evaluating environmental stresses.

Diversity of Gall-Inducing Insects Associated With a Widely Distributed Tropical Tree Species: Testing the Environmental Stress Hypothesis.

Abiotic factors can affect plant performance and cause stress, which in turn affects plant-herbivore interactions. The Environmental Stress Hypothesis (ESH) predicts that gall-inducing insect diversity will be greater on host plants that grow in stressful habitats. We tested this hypothesis, considering both historical and ecological scales, using the plant Copaifera langsdorffii Desf. (Fabaceae) as a model because it has a wide geographic distribution and is a super-host of gall-inducing insects. According to the ESH, we predicted that 1) on a historical scale, the diversity of gall-inducing insects will be higher in habitats with greater environmental stress and 2) on an ecological scale, gall-inducing insect diversity will be greater on plants that possess greater levels of foliar sclerophylly. We sampled gall-inducing insects on plants of C. langsdorffii in five sites with different levels of water and soil nutrient availability and separated from each other by a distance of up to 470 km. The composition, richness, and abundance of gall-inducing insects varied among study sites. Plants located in more stressful habitats had higher levels of foliar sclerophylly; but richness and abundance of gall-inducing insects were not affected by host plant sclerophylly. Habitat stress was a good predictor of gall-inducing insect diversity on a regional scale, thus corroborating the first prediction of the ESH. No relationship was found between plant sclerophylly and gall-inducing insect diversity within habitats. Therefore, on a local scale, we did not find support for our second prediction related to the ESH.

Plant phenological asynchrony and community structure of gall-inducing insects associated with a tropical tree species.

The dynamics of occurrence of target organs in plant populations produces windows of opportunity that directly and indirectly affect the structure of herbivore communities. However, mechanisms that drive herbivore specialization between resource patches are still poorly known. In this study, we tested three hypotheses related to variation in host plant phenology and community structure (i.e., composition, richness, and abundance) of gall-forming species: (a) plants with early leaf-flushing in the season will have greater vegetative growth and high contents of secondary chemical compounds; (b) gall-inducing insect community structure changes among temporary resource patches of the host; and (c) interspecific competition is a probable mechanism that drives gall-inducing insect community structure on Copaifera langsdorffii. We monitored daily a total of 102 individuals of the super-host C. langsdorffii from August 2012 to May 2013, to characterize the leaf flushing time of each host plant. The leaf flushing time had a positive relationship with the number of folioles per branch and a negative relationship with branch growth. We sampled a total of 4,906 galls belonging to 24 gall-inducing insect species from 102 individuals of C. langsdorffii. In spite of some gall-inducing species presented high abundance on early leaf-flushing plants, direct and indirect effects of plant phenology on galling insect abundance was species dependent. At the community level, our study revealed that the quality and quantity of plant resources did not affect the richness and abundance of gall-inducing insects associated with C. langsdorffii. However, the richness and composition of gall-inducing species varied according to the variation in leaf flushing time of the host plant. The results of null model analysis showed that galls co-occurrence on C. langsdorffii trees differ more than expected by chance and that interspecific competition can be one potential mechanism structuring this gall-inducing insect community.

Landscape genetics reveals inbreeding and genetic bottlenecks in the extremely rare short-globose cacti Mammillaria pectinifera (Cactaceae) as a result of habitat fragmentation.

Mammillaria pectinifera is an endemic, short-globose cactus species, included in the IUCN list as a threatened species with only 18 remaining populations in the Tehuacán-Cuicatlán Valley in central Mexico. We evaluated the population genetic diversity and structure, connectivity, recent bottlenecks and population size, using nuclear microsatellites. M. pectinifera showed high genetic diversity but some evidence of heterozygote deficiency (FIS ), recent bottlenecks in some populations and reductions in population size. Also, we found low population genetic differentiation and high values of connectivity for M. pectinifera, as the result of historical events of gene flow through pollen and seed dispersal. M. pectinifera occurs in sites with some degree of disturbance leading to the isolation of its populations and decreasing the levels of gene flow among them. Excessive deforestation also changes the original vegetation damaging the natural habitats. This species will become extinct if it is not properly preserved. Furthermore, this species has some ecological features that make them more vulnerable to disturbance such as a very low growth rates and long life cycles. We suggest in situ conservation to prevent the decrease of population sizes and loss of genetic diversity in the natural protected areas such as the Tehuacán-Cuicatlán Biosphere Reserve. In addition, a long-term ex situ conservation program is need to construct seed banks, and optimize seed germination and plant establishment protocols that restore disturbed habitats. Furthermore, creating a supply of living plants for trade is critical to avoid further extraction of plants from nature.

Patterns of infection by intestinal parasites in sympatric howler monkey (Alouatta palliata) and spider monkey (Ateles geoffroyi) populations in a tropical dry forest in Costa Rica.

In primate populations, endoparasite species richness and prevalence are associated with host traits such as reproductive and social status, age, sex, host population density, and environmental factors such as humidity. We analyzed the species richness and prevalence of intestinal parasites in two sympatric primate populations, one of Alouatta palliata and one of Ateles geoffroyi, found in a tropical dry forest in Costa Rica. We identified three species of intestinal parasites (Controrchis sp., Trypanoxyuris sp., and Strongyloides sp.) in these two primate species. We did not find any differences in species richness between the primate species. However, the prevalences of Controrchis sp. and Trypanoxyuris sp. were higher in Alouatta palliata. Similarly, males and lactating females of Alouatta palliata showed higher Controrchis sp. prevalences. We did not observe any differences in parasite richness and prevalence between seasons. Infectious diseases in endangered primate populations must be considered in conservation strategies, especially when defining protected areas.

Interactions among three trophic levels and diversity of parasitoids: a case of top-down processes in Mexican tropical dry forest.

The objective of this study was to analyze the relationship between plant hosts, galling insects, and their parasitoids in a tropical dry forest at Chamela-Cuixmala Biosphere Reserve in western Mexico. In 120 transects of 30 by 5 m (60 in deciduous forest and 60 in riparian habitats), 29 galling insects species were found and represented in the following order: Diptera (Cecidomyiidae, which induced the greatest abundance of galls with 22 species; 76%), Homoptera (Psylloidea, 6.9%; Psyllidae, 6.9%; Triozidae, 3.4%), Hymenoptera (Tanaostigmatidae, 3.4%; which were rare), and one unidentified morphospecies (3.4%). In all cases, there was a great specificity between galling insect species and their host plant species; one galling insect species was associated with one specific plant species. In contrast, there was no specificity between parasitoid species and their host galling insect species. Only 11 species of parasitoids were associated with 29 galling insect species represented in the following families: Torymidae (18.2%), Eurytomidae (18.2%), Eulophidae (18.2%), Eupelmidae (9.1%), Pteromalidae (9.1%), family Braconidae (9.1%), Platygastridae (9.1%), and one unidentified (9.1%). Most parasitoid species parasitized several gall species (Torymus sp.: 51.1%, Eurytoma sp.: 49.7%, Torymoides sp.: 46.9%). Therefore, the effects of variation in plant defenses do not extend to the third trophic level, because a few species of parasitoids can determine the community structure and composition of galling insect species in tropical plants, and instead, top-down processes seem to be regulating trophic interactions of galling insect species in tropical gall communities.