Biology subjects

Donoso, D. A.

Publications and source records attributed to Donoso, D. A..

8 recordsLinked to original sources

bioRxiv2026

Overgrazing drives ant diversity loss and community homogenization in the Tumbesian dry forest in Ecuador

Tropical dry forests are among the worlds most threatened ecosystems, having lost over 60% of their original extent due to agricultural expansion and livestock grazing. Despite a growing body of research on the effects of deforestation and habitat fragmentation, the consequences of overgrazing on ant communities remain poorly documented, particularly in the Tumbesian bioregion, where uncontrolled goat grazing continues to be the primary disturbance with detrimental effects to plant communities and all the life they support. We sampled ant communities across a goat grazing gradient in a Tumbesian dry forest in Loja, Ecuador. Nine sampling clusters were distributed across a 20 x 25 km landscape on three levels of grazing degradation (low, moderate, and high). Within each cluster, we established three 60 x 60 m plots separated by at least 250 m from each other. Eighteen pitfall traps were deployed per plot. Ant community responses to goat grazing were assessed using abundance- and incidence-based analyses and quantified vegetation structure with satellite-derived NDVI. We collected 47,473 individuals (abundance) in 1,871 collection events (incidence) representing 22 species in six ant subfamilies. Species richness declined with grazing degradation (low = 20 spp.; moderate = 15; high = 13), and generalist forager species dominated the more degraded landscape. Beta diversity decomposition revealed a shift from turnover-dominated dissimilarity at the low moderate degradation transition to nestedness-dominated dissimilarity at the moderate high transition, indicating increasing habitat simplification with higher land degradation. While changes in community composition showed a non-significant trend along the land degradation gradient, our trait-based analysis evidenced effects on the functional space occupied by ants: under High degradation level intensity, ants became smaller, smoother and darker. These findings underscore the conservation value of pristine and low degradation forests and support grazing exclusion as a precautionary component of restoration strategies.

ecology↗

bioRxiv2025

Bumble bees (Hymenoptera: Apidae) of Ecuador

Bumble bee diversity and distribution in the Tropical Andes remain insufficiently documented. Here, we provide the first comprehensive checklist of Bombus species for continental Ecuador, integrating data from regional museum collections, published literature, and online biodiversity databases. We further assessed Cytochrome c oxidase subunit I (COI) barcode variation in six species. In total, we documented 15 Bombus species occurring across 22 provinces of continental Ecuador. Relative to previous reports, we extend the known elevational ranges of B. transversalis and B. funebris to higher altitudes, and of B. excellens to lower elevations. Three species (B. mexicanus, B. coccineus, and B. ephippiatus) were excluded from the checklist, as earlier records are now considered erroneous. Additionally, citizen science data revealed interactions between eight bumble bee species and 138 plant species, of which 87 species are native. Our findings highlight the value of integrating natural history collections, molecular approaches, and participatory science to secure the long-term conservation of bumble bee diversity in the Tropical Andes.

zoology↗

bioRxiv2025

leafing phenology and insect seasonality in an ever-wet tropical forest

Seasonal patterns in tropical insect communities remain poorly understood because temperature is rarely limiting to growth or reproduction in tropical climates. In these regions, insect seasonality is often attributed to rainfall, yet distinct seasonal dynamics also occur in ever-wet forests where climatic fluctuations are minimal. Here, we examine the seasonality of abundance and diversity in lepidopteran herbivores associated with the tropical tree genus Inga in Yasuni, an aseasonal lowland rainforest in the Ecuadorian Amazon. We find that both leaf production and herbivore communities show pronounced seasonal peaks during the driest and brightest months of the year. Using structural equation modeling, we evaluate the relative roles of climate and leaf production in shaping insect seasonality and find support for both pathways. Finally, we show that communities feeding on expanding versus mature leaves differ strongly in composition, with expanding leaves supporting more specialized and phylogenetically divergent herbivore assemblages. Together, these results demonstrate that even in an ever-wet tropical forest, subtle climatic cues and host phenology interact to drive pronounced insect seasonality

ecology↗

bioRxiv2025

The magnitude of cryptic insect diversity in one tropical rainforest

O_LICryptic species represent significant entities in conservation planning and are common among tropical insects. Many studies focusing on cryptic species have been restricted to a narrow taxon and it is not clear whether some insect clades or assemblages may have a greater propensity for cryptic speciation than others. Here, we contrast cryptic diversity among 22 insect assemblages surveyed on Barro Colorado Island (BCI), a tropical rainforest in Panama. C_LIO_LICryptic species were defined as externally indistinguishable from their sister species but with a different barcode index number. We detected 214 cryptic species out of a total of 2,006 species studied (10.6%). The percentage of cryptic species varied greatly among assemblages (0-19%), with half of assemblages devoid of cryptic species, and the highest proportions of cryptics in Pieridae and Formicidae. C_LIO_LIThe percentage of cryptic species was weakly influenced by phylogeny and it was best explained by the local number of species and an index of taxonomic knowledge. Cryptic species were distinguished by an average distance divergence in sequence of 9%, but their ecological characteristics remain unclear. C_LIO_LIAsymptotic estimates indicated that 11.4% of species studied on BCI may be cryptic. Since many of the species-rich insect assemblages occurring on BCI were not considered in this study, this estimate probably represents a lower bound to the true cryptic insect richness on BCI. C_LIO_LIThis significant contribution to biodiversity should not be ignored and, because of apparent low population levels, may be particularly vulnerable to land use and climate changes. C_LI

evolutionary biology↗

bioRxiv2024

Passive accumulation of alkaloids in putatively non-toxic frogs challenges paradigms of the origins of acquired chemical defenses

Understanding the origins of novel, complex phenotypes is a major goal in evolutionary biology. Poison frogs of the family Dendrobatidae have evolved the novel ability to acquire alkaloids from their diet for chemical defense at least three times. However, taxon sampling for alkaloids has been biased towards colorful species, without similar attention paid to inconspicuous ones that are often assumed to be undefended. As a result, our understanding of how chemical defense evolved in this group is incomplete. Here we provide new data showing that, in contrast to previous studies, species from each undefended poison frog clade have measurable yet low amounts of alkaloids. We confirm that undefended dendrobatids regularly consume mites and ants, which are known sources of alkaloids. Thus, our data suggest that diet is insufficient to explain the defended phenotype. Our data support the existence of a phenotypic intermediate between toxin consumption and sequestration -- passive accumulation -- that differs from sequestration in that it involves no derived forms of transport and storage mechanisms yet results in low levels of toxin accumulation. We discuss the concept of passive accumulation and its potential role in the origin of chemical defenses in poison frogs and other toxin-sequestering organisms. In light of ideas from pharmacokinetics we incorporate new and old data from poison frogs into an evolutionary model that could help explain the origins of acquired chemical defenses in animals and provide insight into the molecular processes that govern the fate of ingested toxins. ResumenComprender los origenes de fenotipos novedosos y complejos es un objetivo central en biologia evolutiva. Las ranas venenosas de la familia Dendrobatidae han desarrollado una novedosa habilidad para adquirir alcaloides de su dieta como defensas quimicas, al menos tres veces. Sin embargo, el muestreo de taxones en busca de alcaloides ha estado sesgado hacia las especies coloridas, sin prestar atencion similar a las poco conspicuas que a menudo se presume, no tienen defensas. Como resultado, nuestra comprension de como evolucionan las defensas quimicas en este grupo es incompleta. Aqui, proporcionamos nuevos datos que muestran que, en contraste con estudios anteriores, las especies de cada clado de ranas venenosas no defendidas tienen cantidades bajas pero cuantificables de alcaloides. Confirmamos que los dendrobatidos no defendidos consumen regularmente acaros y hormigas, que son fuentes conocidas de alcaloides. Por lo tanto, nuestros datos sugieren que la dieta es insuficiente para explicar el fenotipo defendido. Nuestros datos respaldan la existencia de un fenotipo intermedio entre consumo y secuestro de toxinas (acumulacion pasiva), que difiere del secuestro en que no implica formas derivadas de mecanismos de transporte y almacenamiento, pero da lugar a bajos niveles de acumulacion de toxinas. Discutimos el concepto de acumulacion pasiva y su potencial rol en el origen de defensas quimicas en ranas venenosas y otros organismos que secuestran toxinas. Considerando ideas de farmacocinetica, incorporamos datos nuevos y antiguos de ranas venenosas dentro de un modelo evolutivo que podria ayudar a explicar los origenes de defensas quimicas adquiridas en animales, y proporcionar una vision de los procesos moleculares que regulan el destino de las toxinas ingeridas.

evolutionary biology↗

bioRxiv2024

Reassembly of a tropical rainforest ecosystem: A new chronosequence in the Ecuadorian Choco tested with the recovery of tree attributes

From hunting and foraging to clearing land for agriculture, humans modify forest biodiversity, landscapes, and climate. Forests constantly undergo disturbance-recovery dynamics and understanding them is a major objective of ecologists and conservationists. Chronosequences are a useful tool for understanding global restoration efforts. They represent a space-for-time substitution approach suited for the quantification of the resistance of ecosystem properties to withstand disturbance and the resilience of these properties until reaching pre-disturbance levels. Here we introduce a newly established chronosequence with 62 plots (50 50 m) in active cacao plantations and pastures, early and late regeneration, and mature old-growth forests, across a 200 km2 area in the extremely wet Choco rainforest. Our chronosequence covers by far the largest total area of plots compared to others in the Neotropics. Plots ranged from 159-615 masl in a forested landscape with 74 {+/-} 2.8 % forest cover within a 1-km radius including substantial old-growth forest cover. Land-use legacy and regeneration time were not confounded by elevation. We tested how six forest structure variables (maximum tree height and DBH, basal area, number of stems, vertical vegetation heterogeneity, and light availability), aboveground biomass (AGB), and rarefied tree species richness change along our chronosequence. Forest structure variables, AGB, and tree species richness increased with regeneration time and are predicted to reach similar levels to those in old-growth forests after ca. 30-116, 202, and 108 yrs, respectively. Compared to previous work in the Neotropics, old-growth forests in Canande accumulate high AGB that takes one of the largest time spans reported until total recovery. Our chronosequence comprises one of the largest tree species pools, covers the largest total area of regenerating and old-growth forests, and has higher forest cover than other Neotropical chronosequences. Hence, our chronosequence can be used to determine the time for recovery and stability (resistance and resilience) of different taxa and ecosystem functions, including species interaction networks. This integrative effort will ultimately help to understand how one of the most diverse forests on the planet recovers from large-scale disturbances.

ecology↗

bioRxiv2022

Poison frog diet and chemical defense are influenced by availability and selectivity for ants

The ability to use small molecule alkaloids as defensive chemicals, often acquired via trophic interactions, has evolved in many organisms. Animals with diet-derived defenses must balance food choices to maintain their defense reservoirs along with other physiological needs. Poison frogs accumulate skin alkaloids from their arthropod diet, but whether they show preference for specific prey remains unexplored. Here, we explore the role of leaf litter prey availability and diet preferences in shaping poison frog chemical defenses along a geographic gradient. We examined skin alkaloid composition, stomach contents and leaf litter ants in aposematic diablito frogs (Oophaga sylvatica) at five sites in northwestern Ecuador, and in sympatric, cryptic Chimbo rocket frogs (Hyloxalus infraguttatus) at one site. We found that differential availability of leaf litter ants influenced alkaloid profiles across diablito populations, and low levels of alkaloids were observed in the sympatric, undefended Chimbo rocket frog. Ants were the primary dietary component of the defended species, while undefended species ate other prey categories including beetles and larvae in addition to ants. A prey selection analysis suggested that defended and undefended frogs both feed on a high proportion of specific small ant genera that naturally contain alkaloids, suggesting that selectivity for toxic prey is not restricted to classically aposematic and highly toxic species. These findings suggest that poison frogs use of feeding resources relative to availability may be an understudied and important selection factor in the evolution of acquired defenses. ResumenLa capacidad de usar alcaloides como productos quimicos defensivos ha evolucionado en muchos organismos, a menudo a traves de interacciones troficas. Los animales con defensas que se derivan de la dieta deben balancear la seleccion de los alimentos para mantener sus reservas defensivas junto con otras necesidades fisiologicas. Las ranas venenosas acumulan alcaloides en la piel procedentes de su dieta de artropodos, pero aun no se ha explorado si muestran preferencia por presas especificas. En este estudio, investigamos el papel de la disponibilidad de presas en la hojarasca y las preferencias dietarias en la configuracion de las defensas quimicas de las ranas venenosas a lo largo de un gradiente geografico. Examinamos la composicion de alcaloides en la piel, el contenido estomacal y la presencia de hormigas de la hojarasca en ranas aposematicas diablito (Oophaga sylvatica) en cinco sitios del noroeste de Ecuador, asi como en la especie criptica y simpatrica rana cohete de Chimbo (Hyloxalus infraguttatus) en un sitio. Encontramos que la disponibilidad diferencial de hormigas en la hojarasca influyo en los perfiles de alcaloides en las poblaciones de diablito, y se detectaron niveles bajos de alcaloides en la rana cohete de Chimbo, previamente considerada indefensa. Las hormigas fueron el componente principal de la dieta en la especie defendida, mientras que la especie indefensa consumio otras categorias de presas, incluidos escarabajos y larvas, ademas de hormigas. Un analisis de seleccion de presas indico que tanto las ranas defendidas como las indefensas prefieren ciertos generos de hormigas pequenas que contienen alcaloides de forma natural, lo que sugiere que la preferencia por presas toxicas no esta restringida a especies clasicamente aposematicas y altamente toxicas. Estos hallazgos sugieren que las preferencias de comportamiento pueden ser un factor de seleccion poco estudiado, pero crucial, en la evolucion de las defensas adquiridas.

ecology↗

bioRxiv2019

Land use impacts poison frog chemical defenses through changes in leaf litter ant communities

Much of the worlds biodiversity is held within tropical rainforests, which are increasingly fragmented by agricultural practices. In these threatened landscapes, there are many organisms that acquire chemical defenses from their diet and are therefore intimately connected with their local food webs. Poison frogs (Family Dendrobatidae) are one such example, as they acquire alkaloid-based chemical defenses from their diet of leaf litter ants and mites. It is currently unknown how habitat fragmentation impacts chemical defense across trophic levels, from arthropods to frogs. We examined the chemical defenses and diets of the Diablito poison frog (Oophaga sylvatica), and the diversity of their leaf litter ant communities in secondary forest and reclaimed cattle pasture. Notably, this research was performed in collaboration with two high school science classrooms. We found that the leaf litter of forest and pasture frog habitats differed significantly in ant community structure. We also found that forest and pasture frogs differed significantly in diet and alkaloid profiles, where forest frogs contained more of specific alkaloids and ate more ants in both number and volume. Finally, ant species composition of frog diets resembled the surrounding leaf litter, but diets were less variable. This suggests that frogs tend to consume particular ant species within each habitat. To better understand how ants contribute to the alkaloid chemical profiles of frogs, we chemically profiled several ant species and found some alkaloids to be common across many ant species while others are restricted to a few species. At least one alkaloid (223H) found in ants from disturbed sites was also found in skins from pasture. Our experiments are the first to link anthropogenic land use changes to dendrobatid poison frog chemical defenses through variation in leaf litter communities, which has implications for conservation management of these threatened amphibians.

ecology↗