Olivia Sanllorente

A geographical mosaic of coevolution in a slave-making host–parasite system

Three different isolated populations of the slave‐making ant Rossomyrmex minuchae, sympatric with its obligate host Proformica longiseta, are known from the high mountains of southern Spain. To test the prediction that the slave‐maker and its host represent a coevolutionary geographical mosaic, we studied the variation in the cuticular hydrocarbons (CHCs) as the trait most likely to show the selection mosaic, plus trait remixing by the gene flow in the populations of each species by means of microsatellites. We found within populations, host and parasite had more similar CHC profiles than between the populations or between parasites and allopatric hosts. The differences between the CHC profiles of the host and parasite, which may be responsible for the level of tolerance towards the parasite, varied between the populations suggesting the existence of a selection mosaic of coevolution. Furthermore, P. longiseta showed higher gene flow than R. minuchae, which would allow local variation in the coevolution of the host and parasite while allowing some trait remixing.

Does Nest Predation Risk Induce Parent Birds to Eat Nestlings' Fecal Sacs? An Experimental Study

Adult birds are frequently observed consuming nestling feces. However, fecal sac ingestion has received little attention, including a lack of experimental tests to understand such behavior. Traditionally, it has been explained by the “parental nutrition hypothesis” (parents acquire nutrients and energy) or the “economic disposal hypothesis” (parents save time to do other tasks). Here, we propose a third explanation, the “nest predation hypothesis”: parents ingest fecal sacs to reduce nest detectability in the presence of a nest predator. We experimentally manipulated the nest-predation risk perceived by adult common blackbirds (Turdus merula). We detected an effect of brood size in the removed and ingested feces while our experiment did not increase fecal sac comsumption. However, we found other evidences supporting that nest predation could play a more subtle role in this parental care behavior: (1) both sexes contributed equally to fecal ingestion; (2) adults ingested more feces in the population with the highest nest-predation risk; and (3) parents that ate fecal sacs increased their permanence at the nest.

Extreme population differentiation in a vulnerable slavemaking ant with a fragmented distribution.

Understanding levels of population differentiation and inbreeding are important issues in conservation biology, especially for social Hymenoptera with fragmented and small population sizes. Isolated populations are more vulnerable to genetic loss and extinction than those with extended continuous distributions. However, small populations are not always a consequence of a recent reduction of their habitat. Thus, determining the history of population isolation and current patterns of genetic variation of a species is crucial for its conservation. Rossomyrmex minuchae is a slave-making ant with patchy distribution in South Eastern Spain and is classified as vulnerable by the IUCN. In contrast, the other three known species of the genus are presumed to show more uniform distributions. Here we investigate the genetic diversity and population structure of R. minuchae and compare it with that found in two other species of the genus: R. anatolicus and R. quandratinodum. We conclude that although genetic diversity of R. minuchae is low, there is no evidence of a recent bottleneck, suggesting a gradual and natural fragmentation process. We also show extreme population differentiation at nuclear and mitochondrial markers, and isolation by distance at a local scale. Despite some evidence for inbreeding and low genetic variation within populations, we found almost no diploid males, a finding which contrasts with that expected in inbred Hymenoptera with single locus complementary sex determination. This could mean that sex is determined by another mechanism. We argue that continued low population size means that detrimental effects of inbreeding and low genetic variation are likely in the future. We suggest that a policy of artificial gene flow aimed at increasing within population variation is considered as a management option.

The ant genomes have been invaded by several types of mariner transposable elements

To date, only three types of full-length mariner elements have been described in ants, each one in a different genus of the Myrmicinae subfamily: Sinvmar was isolated from various Solenopsis species, Myrmar from Myrmica ruginodis, and Mboumar from Messor bouvieri. In this study, we report the coexistence of three mariner elements (Tnigmar-Si, Tnigmar-Mr, and Tnigmar-Mb) in the genome of a single species, Tapinoma nigerrimum (subfamily Dolichoderinae). Molecular evolutionary analyses of the nucleotide sequence data revealed a general agreement between the evolutionary history of most the elements and the ant species that harbour them, and suggest that they are at the vertical inactivation stage of the so-called Mariner Life Cycle. In contrast, significantly reduced levels of synonymous divergence between Mboumar and Tnigmar-Mb and between Myrmar and Botmar (a mariner element isolated from Bombus terrestris), relative to those observed between their hosts, suggest that these elements arrived to the species that host them by horizontal transfer, long after the species’ split. The horizontal transfer events for the two pairs of elements could be roughly dated within the last 2 million years and about 14 million years, respectively. As would be expected under this scenario, the coding sequences of the youngest elements, Tnigmar-Mb and Mboumar, are intact and, thus, potentially functional. Each mariner element has a different chromosomal distribution pattern according to their stage within the Mariner Life Cycle. Finally, a new defective transposable element (Azteca) has also been found inserted into the Tnigmar-Mr sequences showing that the ant genomes have been invaded by at least four different types of mariner elements.

Nest composition and worker relatedness in three slave‐making ants of the genus Rossomyrmex Arnoldi and their Proformica Ruzsky hosts (Hymenoptera, Formicidae)

Abstract  In this paper, we analyze and compare nest composition and architecture as well as worker relatedness in three related species of slave‐making ants: Rossomyrmex anatolicus, R. minuchae, and R. quandratinodum. Colony structure within nests is an important trait in ants, especially in the case of mixed societies, when host and parasite coexist in the same nest. Data for their respective free‐living hosts, Proformica korbi, P. longiseta and P. sp., are also provided. For our study, we integrated a meticulous excavation procedure with a genetic method. We conclude that the average number of parasites, as well as of slaves, is species‐specific, whereas nest depth depends on the nest architecture of the host. The genus Rossomyrmex seems to be monogynous and monandrous, whereas Proformica shows differences in the number of queens and mating frequency. R. quandratinodum shows different traits in nest composition (host/parasite ratio: P/R) and architecture. The difference in traits may account for some differences in parasitism: raid process or avoidance of parasitism.

Molecular cytogenetic studies in the ladybird beetle Henosepilachnaargus Geoffroy, 1762 (Coleoptera, Coccinellidae, Epilachninae).

Abstract The ladybird Henosepilachna argus Geoffroy, 1762 has been cytogenetically studied. In addition we have conducted a review of chromosome numbers and the chromosomal system of sex determination available in the literature in species belonging to the genus Henosepilachna and in its closely related genus Epilachna. Chromosome number of Henosepilachna argus was 2n=18, including the sex chromosome pair, a common diploid chromosome number within the tribe Epilachnini. The study of prophase I meiotic chromosomes showed the typical Xyp “parachute” bivalent as in the majority of species of Coccinellidae. C-banding and fluorescent staining with AT-specific DAPI fluorochrome dye have been carried out for the first time in H. argus. C-banding technique revealed that heterochromatic blocks are pericentromerically located and DAPI staining showed that this heterochromatin is AT rich. Fluorescence in situ hybridizations using rDNA and the telomeric TTAGG sequence as probes have been carried out. FISH using rDNA showed that the nucleolar organizing region is located on the short arm of the X chromosome. FISH with the telomeric sequence revealed that in this species telomeres of chromosomes are composed of the pentanucleotide TTAGG repeats. This is the first study on the telomeric sequences in Coccinellidae.

Rossomyrmex, the slave-maker ants from the arid steppe environments

The host-parasite genera Proformica-Rossomyrmex present four pairs of species with a very wide range of distribution from China to Southeastern Spain, from huge extended plains to the top of high mountains. Here we review (1) the published data on these pairs in comparison to other slave-makers; (2) the different dispersal ability in hosts and parasites inferred from genetics (chance of migration conditions the evolutionary potential of the species); (3) the evolutionary potential of host and parasite determining the coevolutionary process in each host-parasite system that we treat to define using cuticular chemical data. We find a lower evolutionary potential in parasites than in hosts in fragmented populations, where selective pressures give advantage to a limited female parasite migration due to uncertainty of locating a host nest. A similar evolutionary potential is detected for hosts and parasites when the finding of host nests is likely (i.e., in continuous and extended populations). Moreover, some level of local adaptation at CHC profiles between host and parasite exists independently of the kind of geographic distribution and the ability of dispersal of the different populations. Similarity at CHC profiles appears to be a trait imposed by natural selection for the interaction between hosts and slave-makers.

Evolutionary history of the Azteca-like mariner transposons and their host ants

Three different complete mariner elements were found in the genome of the ant Tapinoma nigerrimum. One (Tnigmar-Mr) was interrupted by a 900-bp insertion that corresponded to an incomplete member of a fourth mariner element, called Azteca. In this work, we isolate and characterize full-length Tnigmar-Az elements in T. nigerrimum. The purpose of this study is to clarify the evolutionary history of Azteca elements and their hosts as well as the possible existence of horizontal transfer processes. For this, Azteca-like elements were also retrieved from the available sequences of various ant genomes, representing four different ant subfamilies: Dolichoderinae, Formicinae, Myrmicinae, and Ponerinae. The tree topology resulting for the Azteca-like elements bore very little resemblance to that of their respective hosts. The pervasive presence of Azteca-like elements in all ant genomes, together with the observation that extant copies are usually younger than the genomes that host them, could be explained either by lineage sorting or by recent horizontal transfer of active elements. However, the finding of closer genetic relationships between elements than between the ants that host them is consistent with the latter scenario. This is clearly observed in Sinvmar-Az, Tnigmar-Az, Acepmar-Az, and Cflomar-Az elements, suggesting the existence of horizontal transfer processes. On the contrary, some elements displayed more divergence than did the hosts harboring them. This may reflect either further horizontal transfer events or random lineage sorting.

The spatial distribution does not affect host–parasite coevolution in Rossomyrmex ants

Host and parasite distributions are crucial to understand the coevolutionary outcomes of their relationships. This comes from the fact that the distribution of a species (fragmented vs. continuous habitats) influences its dispersal opportunities. In this work, we studied the effect of the spatial distribution on dispersal and coevolution between three species of social parasite ants of the genus Rossomyrmex (one distributed in high mountains in Spain and two distributed in extended plains in Turkey and Kazakhstan) and their ant hosts Proformica. We analysed the variation at the mitochondrial gene cytochrome c oxidase (COI) to infer female dispersal for parasites as well as the cuticular hydrocarbons (CHCs) of parasites and hosts to study their coevolutionary process, given that CHCs are involved in nestmate recognition. Our genetic results revealed a surprising scarce variation at COI for the three parasite species, suggesting selective forces that prevent from mutation fixation. Therefore, COI appeared to be a poor tool to study dispersal. Furthermore, chemical results showed population differentiation for all host–parasite systems, pointing that coevolution would take place at a local scale regardless of the spatial distribution or dispersal opportunities of the counterparts.

Diferencias en el potencial evolutivo de las hormigas hospedadoras del género Proformica y sus parásitas esclavistas Rossomyrmex (Hymenoptera: Formicidae)

Fallas Henriquez, A., Molina-Murillo, S. 2017. Methodological proposal to quantify and to compensate the agroecosystem services generated by the good agricultural practices of small-farmers. Ecosistemas 26(3): 89-102. Doi.: 10.7818/ECOS.2017.26-3.11 A diversified and less intensive management of agricultural systems produces agroecosystem services that are often not estimated nor compensated in developing countries. The main objective of this study was to create a tool that allows quantification of agroecosystemic services (SAgro) generated in agroforestry peasant farms, and additionally estimate compensation values. Following an initial test in 2013 on 10 farms, an important bibliographical review was carried out, the consultation of experts, and the evaluation in 2015 of 50 farms at the national level, most of them members of the National Agroforestry Union (UNAFOR) of Costa Rica. As a result, a tool was developed to measure in an agile, flexible and economical way the ecosystem services generated by good agricultural practices produced by small producers (peasants) both for their agricultural system as well as the forest system. We also found that the size of farms is not necessarily the determining factor for the production of agroecosystem services, but rather the type of management practices and investments made. In this process, it was estimated that with an average compensation of US