Nest architecture and colony composition in two populations of Ectatomma ruidum sp. 2 (E. ruidum species complex) in southwestern Colombia

Nest architecture plays a fundamental role in the adaptation of ants to their habitat, favoring the action of economically important species. Ectatomma ruidum sp. 2 (ruidum species complex) is a biological control agent in Neotropical agroecosystems, exhibiting high bioturbation impact due to high nest densities. The architecture and composition of 152 nests were studied in two Andean populations of southwestern Colombia, 24 of them being cast using the paraffin wax technique. Nest entrance was a single, circular, 4 mm hole at ground level, without any special external structure, connected to a single vertical tunnel communicating with successive half ellipsoidal chambers. Nests were extremely shallow (depth range: 28.7–35.4 cm), with an average of six chambers and an overall volume of 92.2 cm³ per nest. The deeper the chamber, the smaller its volume. Nest building was independent of plants or roots, and no surface or underground physical connections were found between neighboring nests. Few nests possessed a queen, and neither ergatoids nor microgynes were recorded. Despite significant interactions between localities and the number of both males and workers, queen presence had an overall highly positive effect on the number of workers and larvae and a negative one on the number of gynes. Overall, the studied Colombian populations of E. ruidum sp. 2 retained the simple nest structure described for other species of this species complex and for colonies of the same species from other geographical areas, though they constrasted in their extreme shallowness. Our data suggest that E. ruidum sp. 2, at the local level, does not follow the usual monodomic pattern of this species with facultative polygyny but, rather, has a polydomic pattern with monogyny, perhaps related to the extreme shallowness of the nests due to soil structure, which could significantly enhance the queen’s reproductive inhibition previously reported for this species.

Transformation of coffee-growing landscapes across Latin America. A review

In Latin America, the cultivation of Arabica coffee (Coffea arabica) plays a critical role in rural livelihoods, biodiversity conservation, and sustainable development. Over the last 20 years, coffee farms and landscapes across the region have undergone rapid and profound biophysical changes in response to low coffee prices, changing climatic conditions, severe plant pathogen outbreaks, and other drivers. Although these biophysical transformations are pervasive and affect millions of rural livelihoods, there is limited information on the types, location, and extent of landscape changes and their socioeconomic and ecological consequences. Here we review the state of knowledge on the ongoing biophysical changes in coffee-growing regions, explore the potential socioeconomic and ecological impacts of these changes, and highlight key research gaps. We identify seven major land-use trends which are affecting the sustainability of coffee-growing regions across Latin America in different ways. These trends include (1) the widespread shift to disease-resistant cultivars, (2) the conventional intensification of coffee management with greater planting densities, greater use of agrochemicals and less shade, (3) the conversion of coffee to other agricultural land uses, (4) the introduction of Robusta coffee (Coffea canephora) into areas not previously cultivated with coffee, (5) the expansion of coffee into forested areas, (6) the urbanization of coffee landscapes, and (7) the increase in the area of coffee produced under voluntary sustainability standards. Our review highlights the incomplete and scattered information on the drivers, patterns, and outcomes of biophysical changes in coffee landscapes, and lays out a detailed research agenda to address these research gaps and elucidate the effects of different landscape trajectories on rural livelihoods, biodiversity conservation, and other aspects of sustainable development. A better understanding of the drivers, patterns, and consequences of changes in coffee landscapes is vital for informing the design of policies, programs, and incentives for sustainable coffee production.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13593-021-00712-0.

The Community Ecology of Herbivore Regulation in an Agroecosystem: Lessons from Complex Systems

Whether an ecological community is controlled from above or below remains a popular framework that continues generating interesting research questions and takes on especially important meaning in agroecosystems. We describe the regulation from above of three coffee herbivores, a leaf herbivore (the green coffee scale, Coccus viridis), a seed predator (the coffee berry borer, Hypothenemus hampei), and a plant pathogen (the coffee rust disease, caused by Hemelia vastatrix) by various natural enemies, emphasizing the remarkable complexity involved. We emphasize the intersection of this classical question of ecology with the burgeoning field of complex systems, including references to chaos, critical transitions, hysteresis, basin or boundary collision, and spatial self-organization, all aimed at the applied question of pest control in the coffee agroecosystem.

Context dependent life-history shift in Macrodinychus sellnicki mites attacking a native ant host in Colombia

Ant parasitoidism has been reported in seven of the 26 recognized species of the mite genus Macrodinychus (Machrodynichidae). Macrodynichus sellnicki, previously reported as a parasitoid of the invasive ant Nylanderia fulva in Colombia, is now reported, in the same region, as attacking a native host, Ectatomma sp. 2 (E. ruidum complex). The mite develops within the protective silk cocoon of an Ectatomma pupa and waits for the emergence of the young ant before leaving the cocoon, unmolested. Overall nest prevalence was relatively high (34.6% of the 52 nests containing cocoons) but pupae prevalence was low (4.0%, n = 1401 cocoons). Mite life-history (parasite or parasitoid) was context dependent, shifting according to the intensity of the attack on a same host. Contrary to the strictly parasitoidic association of M. sellnicki with N. fulva, single mite attacks against E. ruidum did not result in host killing and solitary M. sellnicki (78.6% of the cases) behaved as parasites. However, in 21.4% of the attacks (0.9% of all available host pupae) more than one mite was involved and behaved as parasitoids, draining the host of its internal fluids and killing it. This is the first association of a macrodinychid mite with a species of the subfamily Ectatomminae, and the first ant associated mite for which such a context dependent life-style shift is described.

A comparative study of ant diversity under three coverages in a Neotropical coffee landscape

The coffee cultivation has displaced natural vegetation and its associated biological diversity. The present study describes the diversity of ground-dwelling ants on eight plantations where coffee is grown in the shade (SHD), eight plantations where coffee is grown under unshaded coffee (SUN) and four patches of forest (FOS) in a coffee-growing region of Colombia. The research was conducted in transects composed of 12 sampling stations, each of which employed active collection, pitfall traps and litter sifting. Nine habitat variables were analyzed to characterize each site, and these values were related to the diversity of ants and functional groups. A total of 92 morphospecies were collected. Myrmicinae was the subfamily with the highest representation. The sample coverage presented a deficit of less than 5 %. The rank abundance curves exhibited differences in the ant assemblages. The ant communities found in the forest exhibited greater diversity and a larger number of exclusive species than the communities found in locations of other land uses; the SHD and SUN communities were characterized by 80.3 % and 62.3 %, respectively, of the diversity found in the forest communities. The functional similarity index as adapted for guilds by Sørensen reveals a high degree of similarity in the structure of their ant communities, but less so in their composition.The shaded coffee plantations have a richer and more equitable ant fauna than the exposed coffee plantations, reinforcing the idea that shade cultivation favors the establishment of ant fauna and, consequently, ecological functionality.

Uso de acolchados (mulching) en la restauración de bosques secos en el Valle del Cauca

El bosque seco tropical es uno de los ecosistemas más amenazados por actividades humanas. Pese a eso, los esfuerzos para su restauración son insuficientes. Como en otros bosques tropicales, las gramíneas exóticas constituyen una barrera importante para su regeneración natural. El acolchado (mulch) es una técnica utilizada en el control de plantas arvenses para su evitar la competencia  con los árboles nativos durante el proceso de restauración. Se estudió el efecto de dos acolchados  (vegetal y de cartón) sobre el crecimineto y superviviencia de cuatro especies de plantas nativas (Pithecellobium dulce, Achatocarpus nigricans, Cestrum cf. nocturnum y Croton gossypiifolius).  También se estudió el efecto del acolchado sobre las arvenses y el suelo por seis meses. Se encontró mayor crecimiento en el diámetro bajo el tratamiento de acolchado vegetal. Este tratamiento también  permitió mayor retención de humedad en el suelo en el periodo de menor precipitación. En ambos  acolchados hubo un menor crecimiento de arvenses y se observó la colonización de commelináceas  sobre las áreas tratadas. Se concluye que el uso de acolchados es viable para el control de gramíneas  exóticas  en  áreas  en  restauración.  La  reducción  en  la  variación  en  la  humedad  del  suelo  puede  favorecer el crecimiento de las plantas nativas a largo plazo.

The database of the PREDICTS (Projecting Responses of Ecological Diversity In Changing Terrestrial Systems) project

The PREDICTS project-Projecting Responses of Ecological Diversity In Changing Terrestrial Systems (www.predicts.org.uk)-has collated from published studies a large, reasonably representative database of comparable samples of biodiversity from multiple sites that differ in the nature or intensity of human impacts relating to land use. We have used this evidence base to develop global and regional statistical models of how local biodiversity responds to these measures. We describe and make freely available this 2016 release of the database, containing more than 3.2 million records sampled at over 26,000 locations and representing over 47,000 species. We outline how the database can help in answering a range of questions in ecology and conservation biology. To our knowledge, this is the largest and most geographically and taxonomically representative database of spatial comparisons of biodiversity that has been collated to date; it will be useful to researchers and international efforts wishing to model and understand the global status of biodiversity.

Climate mediates the effects of disturbance on ant assemblage structure

Many studies have focused on the impacts of climate change on biological assemblages, yet little is known about how climate interacts with other major anthropogenic influences on biodiversity, such as habitat disturbance. Using a unique global database of 1128 local ant assemblages, we examined whether climate mediates the effects of habitat disturbance on assemblage structure at a global scale. Species richness and evenness were associated positively with temperature, and negatively with disturbance. However, the interaction among temperature, precipitation and disturbance shaped species richness and evenness. The effect was manifested through a failure of species richness to increase substantially with temperature in transformed habitats at low precipitation. At low precipitation levels, evenness increased with temperature in undisturbed sites, peaked at medium temperatures in disturbed sites and remained low in transformed sites. In warmer climates with lower rainfall, the effects of increasing disturbance on species richness and evenness were akin to decreases in temperature of up to 9°C. Anthropogenic disturbance and ongoing climate change may interact in complicated ways to shape the structure of assemblages, with hot, arid environments likely to be at greatest risk.

Monitoring the Diversity of Hunting Ants (Hymenoptera: Formicidae) on a Fragmented and Restored Andean Landscape

Hunting ants are predators of organisms belonging to different trophic levels. Their presence, abundance, and diversity may reflect the diversity of other ants and contribute to evaluate habitat conditions. Between 2003 and 2005 the restoration of seven corridors in an Andean rural landscape of Colombia was performed. The restoration took place in lands that were formerly either forestry plantations or pasturelands. To evaluate restoration progress, hunting ants were intensely sampled for 7 yr, using sifted leaf litter and mini-Winkler, and pitfall traps in 21 plots classified into five vegetation types: forests, riparian forests, two types of restored corridors, and pasturelands. The ant communities were faithful to their habitat over time, and the main differences in ant composition, abundance, and richness were due to differences among land use types. The forests and riparian forests support 45% of the species in the landscape while the restored corridors contain between 8.3-25%. The change from forest to pasturelands represents a loss of 80% of the species. Ant composition in restored corridors was significantly different than in forests but restored corridors of soil of forestry plantations retained 16.7% more species than restored corridors from pasturelands. Ubiquitous hunting ants, Hypoponera opacior (Forel) and Gnamptogenys ca andina were usually associated with pastures and dominate restored corridors. Other cryptic, small, and specialized hunting ants are not present in the restored corridors. Results suggest that the history of land use is important for the biodiversity of hunting ants but also that corridors have not yet effectively contributed toward conservation goals.

The PREDICTS database: a global database of how local terrestrial biodiversity responds to human impacts

Biodiversity continues to decline in the face of increasing anthropogenic pressures such as habitat destruction, exploitation, pollution and introduction of alien species. Existing global databases of species’ threat status or population time series are dominated by charismatic species. The collation of datasets with broad taxonomic and biogeographic extents, and that support computation of a range of biodiversity indicators, is necessary to enable better understanding of historical declines and to project – and avert – future declines. We describe and assess a new database of more than 1.6 million samples from 78 countries representing over 28,000 species, collated from existing spatial comparisons of local-scale biodiversity exposed to different intensities and types of anthropogenic pressures, from terrestrial sites around the world. The database contains measurements taken in 208 (of 814) ecoregions, 13 (of 14) biomes, 25 (of 35) biodiversity hotspots and 16 (of 17) megadiverse countries. The database contains more than 1% of the total number of all species described, and more than 1% of the described species within many taxonomic groups – including flowering plants, gymnosperms, birds, mammals, reptiles, amphibians, beetles, lepidopterans and hymenopterans. The dataset, which is still being added to, is therefore already considerably larger and more representative than those used by previous quantitative models of biodiversity trends and responses. The database is being assembled as part of the PREDICTS project (Projecting Responses of Ecological Diversity In Changing Terrestrial Systems – http://www.predicts.org.uk). We make site-level summary data available alongside this article. The full database will be publicly available in 2015.

Composting to control the leaf-cutting ant atta cephalotes l. (hymenoptera: formicidae)

Las hormigas cortadoras de hojas, Atta y Acromyrmex, son los herbívoros más importantes en los trópicos. En este estudio se comparan los efectos de dos métodos no químicos sobre la sobrevivencia y actividad de nidos de Atta cephalotes (Formicidae:Myrmicinae). Un total de 83 nidos activos de A. cephalotes fueron asignados de forma aleatoria a uno de tres tratamientos: 1) incorporación de un material compostable al suelo; 2) remoción y mezcla de la capa superficial del suelo (método convencional) y 3) placebo o control (sin tratamiento). Después de tres meses, los porcentajes de nidos eliminados con cada uno de los tratamientos fueron 26,5; 9,6; y 3,6; respectivamente. Un análisis de varianza de medidas repetidas mostró una diferencia significativa entre las colonias de hormigas sometidas a los tratamientos compostado y remoción mecánica en relación con el placebo. Esto debido a la destrucción de las pistas de forrajeo, de las aberturas, cámaras y túneles. Sin embargo, el más fuerte efecto fue observado con el compostado. Basado en estos resultados sobre los nidos de A. cephalotes y su efecto potencial de enriquecer el suelo, el tratamiento compostado puede representar una práctica sustentable y ecológicamente amigable en el control de hormigueros de Atta.

Effect of two agroecological management strategies on ant (Hymenoptera: Formicidae) diversity on coffee plantations in southwestern Colombia

Simplification of agroecosystems because of industrialization of agriculture may cause the loss of associated animal biodiversity of both vertebrates and invertebrates. To measure how the agricultural intensification on coffee plantations affects ant biodiversity, we intensively sampled ants in Caldono (Cauca, Colombia). We surveyed 15 sites classified into three management types: sun coffee plantations, shaded coffee plantations, and forest patches. Fifteen 50-m linear transects, each one consisting of 5 pitfall traps and 5 tuna baits, were set at each sampling location between December of 2009 and February of 2010. We collected 18,186 ants that represent 82 ant species, 34 genera, and 9 subfamilies of Formicidae (Hymenoptera: Formicidae). The management intensification index showed an increasing intensification gradient along the 15 sampling locations from forest patches to shaded coffee to sun coffee plantations. Shaded coffee plantations harbored the highest number of species (60), followed by forest (56) and sun coffee (33). Ant species composition and plant structure on shaded coffee plantations resembled the forest patches more than the sun coffee plantations. Forest and shaded coffee plantations had a more equitable distribution of ant species, whereas in sun coffee plantations, Linepithema neotropicum (Emery) and Ectatomma ruidum (Roger) typically outnumbered all other ant species. Evidence from functional groups indicated that specific habitat and feeding requirements exist among the species that are found together. Our results confirmed that intensification of agriculture negatively affects ant diversity, despite the fact that farms were located in a heterogeneous landscape, suggesting that agroecological management is a strong determinant in the conservation of wild fauna.

Does plant diversity benefit agroecosystems? A synthetic review

Predictive theory on how plant diversity promotes herbivore suppression through movement patterns, host associations, and predation promises a potential alternative to pesticide-intensive monoculture crop production. We used meta-analysis on 552 experiments in 45 articles published over the last 10 years to test if plant diversification schemes reduce herbivores and/or increase the natural enemies of herbivores as predicted by associational resistance hypotheses, the enemies hypothesis, and attraction and repellency model applications in agriculture. We found extensive support for these models with intercropping schemes, inclusion of flowering plants, and use of plants that repel herbivores or attract them away from the crop. Overall, herbivore suppression, enemy enhancement, and crop damage suppression effects were significantly stronger on diversified crops than on crops with none or fewer associated plant species. However, a relatively small, but significantly negative, mean effect size for crop yield indicated that pest-suppressive diversification schemes interfered with production, in part because of reducing densities of the main crop by replacing it with intercrops or non-crop plants. This first use of meta-analysis to evaluate the effects of diversification schemes, a potentially more powerful tool than tallies of significant positive and negative outcomes (vote-counting), revealed stronger overall effects on all parameters measured compared to previous reviews. Our analysis of the same articles used in a recent review facilitates comparisons of vote-counting and meta-analysis, and shows that pronounced results of the meta-analysis are not well explained by a reduction in articles that met its stricter criteria. Rather, compared to outcome counts, effect sizes were rarely neutral (equal to zero), and a mean effect size value for mixed outcomes could be calculated. Problematic statistical properties of vote-counting were avoided with meta-analysis, thus providing a more precise test of the hypotheses. The unambiguous and encouraging results from this meta-analysis of previous research should motivate ecologists to conduct more mechanistic experiments to improve the odds of designing effective crop diversification schemes for improved pest regulation and enhanced crop yield.

[Ants: species-area relationship in tropical dry forest fragments]

We analyzed the effect of fragmentation on ant species-area and specimen frequency-area relationships in nine patches of tropical dry forest in the middle Cauca river basin in Colombia. Species richness and specimen relative frequency of ants were positively correlated with area, whereas no significant correlation was found between species richness and the degree of isolation calculated for the forest patches. As the fragmentation affects different functional groups in different ways, we analyzed the species-area relationship for separate functional groups of ants. According to the habitat requirements we found that the species richness increased faster as area increased for ants inhabiting decomposing wood, followed by ants associated with trees, while species richness of ants living under dead leaves did not correlate with area. According to the food preference, species richness was positively correlated with area for the army ant group, while no significant correlation was found for solitary hunters or for leaf-cutting ants. Ant species richness and specimen density were calculated from equal size samples and examined in relation to the habitat area. An inverse correlation was found only for specimen density, the opposite of what was expected. To our knowledge this is one of the first studies showing differential responses of functional groups of ants to habitat loss. Moreover, it emphasizes the conservation value of small forest fragments for ants in a tropical dry forest.

Biodiversity loss in Latin American coffee landscapes: review of the evidence on ants, birds, and trees

Studies have documented biodiversity losses due to intensification of coffee management (reduction in canopy richness and complexity). Nevertheless, questions remain regarding relative sensitivity of different taxa, habitat specialists, and functional groups, and whether implications for biodiversity conservation vary across regions.We quantitatively reviewed data from ant, bird, and tree biodiversity studies in coffee agroecosystems to address the following questions: Does species richness decline with intensification or with individual vegetation characteristics? Are there significant losses of species richness in coffee-management systems compared with forests? Is species loss greater for forest species or for particular functional groups?and Are ants or birds more strongly affected by intensification? Across studies, ant and bird richness declined with management intensification and with changes in vegetation. Species richness of all ants and birds and of forest ant and bird species was lower in most coffee agroecosystems than in forests, but rustic coffee (grown under native forest canopies) had equal or greater ant and bird richness than nearby forests. Sun coffee(grown without canopy trees) sustained the highest species losses, and species loss of forest ant, bird, and tree species increased with management intensity. Losses of ant and bird species were similar, although losses of forest ants were more drastic in rustic coffee. Richness of migratory birds and of birds that forage across vegetation strata was less affected by intensification than richness of resident, canopy, and understory bird species. Rustic farms protected more species than other coffee systems, and loss of species depended greatly on habitat specialization and functional traits. We recommend that forest be protected, rustic coffee be promoted,and intensive coffee farms be restored by augmenting native tree density and richness and allowing growth of epiphytes. We also recommend that future research focus on potential trade-offs between biodiversity conservation and farmer livelihoods stemming from coffee production.

Enigmatic biodiversity correlations: ant diversity responds to diverse resources

A pattern noted in ecology is that diversity at one level begets diversity at other levels. In the case of consumers competing for similar resources, the diversity of those resources is thought to provide some degree of niche diversification in which a diverse set of consumer species can coexist. If, however, the diverse resources are not sufficiently distinct from one another, from the standpoint of the consumer species, such niche diversification will not exist. We experimentally show that a diverse array of twigs attracted 80% more species of twig-nesting ants than a monospecific collection of twigs. The specific tree species from which the twigs were derived did not explain the pattern. It appears that diversity per se at one level (twigs) creates conditions that promote diversity at another level (nesting ants).