Large-scale mitochondrial DNA analysis of native honey bee Apis mellifera populations reveals a new African subgroup private to the South West Indian Ocean islands

Background: The South West Indian Ocean (SWIO) archipelagos and Madagascar constitute a hotspot of biodiversity with a high rate of endemism. In this area, the endemic subspecies A. m. unicolor has been described in Madagascar. It belongs to the African lineage, one of the four described evolutionary lineages in honey bees. Despite a long beekeeping tradition and several recorded European introductions, few studies have been carried out on the diversity and proportion of honey bee subspecies. In order to identify and define which evolutionary lineages and potential sub-lineages are present in the SWIO, the COI-COII intergenic region and the ND2 gene of the mtDNA were sequenced in honey bee colonies from three archipelagos. An extensive sampling (n = 1184 colonies) was done in the Mascarene (La Réunion, Mauritius, Rodrigues), Seychelles (Mahé, Praslin, La Digue) and Comoros (Grande Comore, Mohéli, Anjouan, Mayotte) archipelagos. Islands genetic diversity was compared to newly sampled populations from Madagascar, continental African and European populations. Results: African lineage haplotypes were found in all islands (except for Rodrigues). Madagascar, Comoros and Seychelles had 100% of A lineage, 95.5% in La Réunion and 56.1% in Mauritius. Among all African colonies detected in the SWIO, 98.1% (n = 633) of COI-COII haplotypes described the presence of the subspecies A. M. unicolor. Both genetic markers revealed i) a new private AI mitochondrial group shared by the SWIO archipelagos and Madagascar distant from continental populations; ii) the private African haplotypes for each island suggested diversity radiation in the archipelagos; iii) the detection of the Comoros archipelago as a possible contact area between insular and continental African populations. The exotic European C and M lineages were only detected in the Mascarene archipelago, but striking differences of proportion were observed among islands. Merely 4.6% of European colonies were found in La Réunion whereas Mauritius cumulated 44%. Here, among the 84 observed COI-COII haplotypes, 50 were newly described including 13 which were private to the SWIO archipelagos and Madagascar. Similarly, 24 of the 34 found ND2 haplotypes were novel which included six haplotypes particular to the SWIO populations. Conclusion: A new African subgroup was described in the SWIO region with mitochondrial genetic evidence that A. m. unicolor is the indigenous subspecies of the archipelagos surrounding Madagascar. (Résumé d'auteur

Genetic diversity and differentiation among insular honey bee populations in the southwest Indian Ocean likely reflect old geographical isolation and modern introductions

With globalization the Western honey bee has become a nearly cosmopolitan species, but it was originally restricted to the Old World. This renowned model of biodiversity has diverged into five evolutionary lineages and several geographic “subspecies.” If Apis mellifera unicolor is indubitably an African subspecies endemic to Madagascar, its relationship with honey bees from three archipelagos in the southwest Indian Ocean (SWIO) hotspot of biodiversity is misunderstood. We compared recent mtDNA diversity data to an original characterization of the nuclear diversity from honey bees in the Mascarenes and Comoros archipelagos, using 14 microsatellites, but also additional mtDNA tRNALeu-cox2 analysis. Our sampling offers the most comprehensive dataset for the SWIO populations with a total of 3,270 colonies from 10 islands compared with 855 samples from Madagascar, 113 from Africa, and 138 from Europe. Comprehensive mitochondrial screening confirmed that honey bees from La Réunion, Mauritius, and Comoros archipelagos are mainly of African origin (88.1% out of 2,746 colonies) and that coexistence with European lineages occurs only in the Mascarenes. PCA, Bayesian, and genetic differentiation analysis showed that African colonies are not significantly distinct on each island, but have diversified among islands and archipelagos. FST levels progressively decreased in significance from European and African continental populations, to SWIO insular and continental populations, and finally among islands from the same archipelago. Among African populations, Madagascar shared a nuclear background with and was most closely related to SWIO island populations (except Rodrigues). Only Mauritius Island presented clear cytoplasmic disequilibrium and genetic structure characteristic of an admixed population undergoing hybridization, in this case, between A. m. unicolor and A. m. ligustica, A. m. carnica and A. m. mellifera-like individuals. Finally, global genetic clustering analysis helped to better depict the colonization and introduction pattern of honey bee populations in these archipelagos. (Résumé d'auteur

Autosomal and mitochondrial adaptation following admixture: a case study on the honeybees of Reunion Island.

The honeybee population of the tropical Reunion Island is a genetic admixture of the Apis mellifera unicolor subspecies, originally described in Madagascar, and of European subspecies, mainly A.m. carnica and A. m. ligustica, regularly imported to the island since the late 19th century. We took advantage of this population to study genetic admixing of the tropical-adapted indigenous and temperate-adapted European genetic backgrounds. Whole genome sequencing of 30 workers and 6 males from Reunion, compared to samples from Europe, Madagascar, Mauritius, Rodrigues and the Seychelles, revealed the Reunion honeybee population to be composed on average of 53.2 ± 5.9% A. m. unicolor nuclear genomic background, the rest being mainly composed of A. m. carnica and to a lesser extent A. m. ligustica. In striking contrast to this, only one out of the 36 honeybees from Reunion had a mitochondrial genome of European origin, suggesting selection has favoured the A. m. unicolor mitotype, which is possibly better adapted to the island's bioclimate. Local ancestry was determined along the chromosomes for all Reunion samples, and a test for preferential selection for the A. m. unicolor or European background revealed 15 regions significantly associated with the A. m. unicolor lineage and 9 regions with the European lineage. Our results provide insights into the long-term consequences of introducing exotic specimen on the nuclear and mitochondrial genomes of locally-adapted populations. (Résumé d'auteur

Kleptoparasitism in the endemic gecko Phelsuma inexpectata: pollen theft from foraging honeybees on Réunion

International audienceInterspecific kleptoparasitism (the stealing of already-procured items from other species) has received little attention in tropical reptiles. We report here the second case of kleptoparasitism in tropical lizards, and the first known case of pollen theft by a vertebrate species. Phelsuma inexpectata, a gekkonid lizard endemic to Réunion, was observed robbing pollen pellets from honeybees (Apis mellifera) foraging on Latania lontaroides flowers. Video-records were used to obtain reliable information on gecko-honeybee interactions occurring on L. lontaroides inflorescences. During the 19 observation periods (total duration 140 min) a total of 78 attempts were recorded, at least 40% were successful. Both males and females displayed kleptoparasitic behaviour. A high level of gecko kleptoparasitism occurred, with an average one-robbery attempt every 2 min. Behaviour of both the kleptoparasitic P. inexpectata and its host A. mellifera are described

Worker thermal tolerance in the thermophilic ant Cataglyphis cursor (Hymenoptera, Formicidae)

In the thermophilic ant genus Cataglyphis, species differing in their physical caste system have developed alternative mechanisms to face extreme heat by physiological and/or behavioural adaptations. In this study, we tested whether thermal tolerance is related to worker size in the ant Cataglyphis cursor that presents intermediate worker size compared with previously studied species (size range 3.5-10 mm). Thermal tolerance at two temperatures was tested in the laboratory on colonies originating from two habitats (seaside versus vineyard), known to differ in average worker size. As expected large workers were more resistant to high temperature than small workers, but the effect of worker size on thermal resistance was less pronounced under the more extreme temperatures. The pattern of thermal tolerance was similar in the two habitat types. After controlling for worker size, worker thermal tolerance significantly varied amongst colonies, but this variation was not related to colony size. Our results suggest that a higher thermal tolerance can confer an advantage to larger workers especially during foraging and are discussed in the context of the evolution of worker size in ants. © Birkḧuser Verlag, Basel/Switzerland 2009.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Evidence of seasonal reproduction, laying site fidelity, and oviposition synchronicity in the critically endangered endemic Manapany Day Gecko (Phelsuma inexpectata) from Reunion Island (western Indian Ocean)

The reproductive phenology of tropical geckos varies considerably between species. We investigated the reproductive timing of Phelsuma inexpectata, a critically endangered tropical squamate endemic to Reunion Island (western Indian Ocean). From February 2018 to August 2020 (30 months), we carried out monthly monitoring of laying sites. Phelsuma inexpectata exhibited a seasonal reproductive pattern, with breeding activity from the end of the austral winter to the end of the austral summer. We observed intra- and interannual synchronicity of oviposition in September. The seasonal  reproductive pattern appears to be synchronized with optimal environmental conditions (temperatures, food resources) for the survival of eggs and hatchlings. Females deposited their eggs in communal laying sites (up to 9 eggs) and exhibited interannual laying site fidelity (50% of the laying sites were reused in the second breeding season). Minimum and maximum incubation periods (± SD) were 69 ± 24 days and 115 ± 25 days, respectively. Our study provides the first description of the Manapany Day Gecko reproduction in the wild and highlights for the first time the very high synchronicity of oviposition in the genus Phelsuma. These results will be very useful to improve the conservation of this species, in particular with regard to the timing of predator control, designing monitoring protocols for breeding and survival parameters, and implementing a captive rearing program for hatchlings

Evidence of seasonal reproduction, laying site fidelity, and oviposition synchronicity in the critically endangered endemic Manapany Day Gecko (Phelsuma inexpectata) from Reunion Island (western Indian Ocean)

International audienceThe reproductive phenology of tropical geckos varies considerably between species. We investigated the reproductive timing of Phelsuma inexpectata, a critically endangered tropical squamate endemic to Reunion Island (western Indian Ocean). From February 2018 to August 2020 (30 months), we carried out monthly monitoring of laying sites. Phelsuma inexpectata exhibited a seasonal reproductive pattern, with breeding activity from the end of the austral winter to the end of the austral summer. We observed intra-and interannual synchronicity of oviposition in September. The seasonal reproductive pattern appears to be synchronized with optimal environmental conditions (temperatures, food resources) for the survival of eggs and hatchlings. Females deposited their eggs in communal laying sites (up to 9 eggs) and exhibited interannual laying site fidelity (50% of the laying sites were reused in the second breeding season). Minimum and maximum incubation periods (± SD) were 69 ± 24 days and 115 ± 25 days, respectively. Our study provides the first description of the Manapany Day Gecko reproduction in the wild and highlights for the first time the very high synchronicity of oviposition in the genus Phelsuma. These results will be very useful to improve the conservation of this species, in particular with regard to the timing of predator control, designing monitoring protocols for breeding and survival parameters, and implementing a captive rearing program for hatchlings

Experience influences aggressive behaviour in the Argentine ant

All animals interact with conspecifics during their life, and nearly all also display some form of aggression. An enduring challenge, however, is to understand how the experiences of an individual animal influence its later behaviours. Several studies have shown that prior winning experience increases the probability of initiating fights in later encounters. Using behavioural assays in the laboratory, we provide evidence that, in Argentine ants (Linepithema humile), the mere exposure to an opponent, without the encounter escalating to a fight, also increases the probability that it will display aggression in later encounters. Argentine ant workers differ in their propensity to attack non-colonymates, with some ants repeatedly aggressive and others consistently more docile. Although 78 per cent of the workers were consistent in their behaviour from one encounter to the next, workers that did change their behaviour after an encounter with a non-colonymate more often changed from non-aggressive to aggressive, rather than the reverse. Surprisingly, a single encounter with a non-colonymate increased a worker's propensity to fight in encounters up to a week later. An encounter with a non-colonymate also increased the probability that a worker would attack ants from a colony that it had not previously encountered. Thus, these interactions lowered the overall aggression threshold, rather than stimulating a specific aggressive response to a particular foreign colony. Finally, our data suggest that aggression towards non-colonymates increases with age