Objectifs :

The aims of the Mitaraka inventory were multiple and can be summarized by the following scientific objectives listed in relative order of priority:

1) To discover new species for science and to describe them in a short time frame;

2) To discover and publish first records (of species known in other countries but not yet reported from French Guiana in the literature) for the French Guianian territory;

3) To update the national (MNHN) and regional reference collections with fresh material;

4) To develop an inventory as complete as possible in a remote site of French Guiana in order to serve as a reference for biogeographical studies and conservation strategies at the scale of the Guyana Shield and, possibly, for the whole Amazonian basin;

5) To manage and share these data with conservation managers and the scientific community within the framework of the French National Inventory of Natural Heritage (INPN: https://inpn.mnhn.fr) and the Global Biodiversity Information Facility (GBIF: https://www.gbif.org/) at the international level;

6) To allow specific research by a few teams of researchers within the framework of ecological study protocols, the Habitats protocol (managed by the Guiana National Park and National Forest Agency), DynForDiv protocol (IRD) and Diadema protocol (LabEx CEBA) to study the link between species communities and forest habitats.

Other, secondary, objectives of the expedition, which were left to the participants' discretion and inspiration, might include comparing different collection methods, documenting observations by means of in situ photographs and/or sound recordings of the species present, publishing new biological observations and/or DNA sequencing of different species for integrative taxonomic approaches.

Contexte scientifique :

State of knowledge on French Guiana species diversity and focal taxa of the expedition

In 2014, a first primary inventory of French Guiana insect species compiled by the MNHN and the Société entomologique Antilles-Guyane (SEAG) was analysed in order to serve as a basis for the national taxonomic reference system TAXREF (Brûlé & Touroult 2014). The following was derived from this database of more than 15,100 valid species names cited from French Guiana in the scientific literature as of 2014 (in November 2017, the updated list had reached 16,620 species, Gargominy et al. 2017). On a global scale, between Carl von Linné (1758) and 2013, the average rate of species descriptions reached about 60 species per year, with the highest peak during the early 20^th century (178 species per year between 1904 and 1908). In the last century, 1960-1970 proved the least productive period. The most recent (analysis of the 2008-2013 period) overall rate of added species is much higher than the average. It has reached about 180 species per year, with ca. 100 new species to science and 80 first records for French Guiana.

Contrary to a widespread belief and an internationally documented phenomenon of decline in taxonomy knowledge (Hopkins & Freckleton 2002), knowledge on insect diversity has been progressing at a relatively high rate in the past 10 years in French Guiana due to combined efforts of some professional taxonomists and the large amateur community involved in collecting material and describing new species.Requests by protected areas managers for faunal surveys, have also offered new opportunities to obtain material from remote sites. However, the taxonomic inventory is far from complete and the current species number is estimated to be around 20% of the extant richness (Brûlé & Touroult, 2014). Richness by taxonomic order in French Guiana was compared with that at the global level (Zhang 2013). Five insect groups appeared to be relatively better studied (and/or possibly more diverse) in French Guiana, compared to the global level: Odonata, Mantodea, Lepidoptera, Blattodea, and to a lesser extent, Dermaptera. Phasmatodea, Coleoptera, Orthoptera and Megaloptera were at a comparable level between French Guiana and the global level. It should be noted that the known richness of the orders in these two categories is still far from being exhaustive, even including Lepidoptera and Odonata. The other 20 orders are underrepresented in the faunal list of French Guiana in comparison to the world level status. They might be either less diverse in French Guiana for large scale biogeographical reasons, or perhaps they have not received as much attention as other taxa. The current steep rate of descriptions in some of these groups (Hymenoptera, Hemiptera) seems to support the second hypothesis. The highly diverse orders, which are obviously understudied in French Guiana, offer the largest opportunity for extensive taxonomic discoveries, and first country records. The first four insect orders are: Diptera, Hymenoptera, Hemiptera and Trichoptera. Although seemingly equally represented in both French Guiana and the world, the megadiverse Coleoptera is certainly, in absolute numbers, one of the orders with most species to be described (Touroult et al., 2014).

In an annotated list of the 453 species of French Guiana spiders, Vedel et al. (2013) also highlighted a very low level of taxonomic knowledge onthis speciose group.

In view of the abovementioned recent assessment of knowledge, the Mitaraka survey and the whole process of studying the collected material had to focus mainly on Diptera, Hymenoptera, Hemiptera and Coleoptera, as far as insects were concerned, and also to treat other invertebrates, such as Arachnids and Annelida. However, knowing that there are also species to be discovered in the better known classes and orders (such as Lepidoptera, Odonata and even herpetofauna and fish) and with the aim of drawing up a reference inventory for this area, a broad taxonomic scope was maintained. Mammals and birds were deliberately not included, although participants were encouraged to list their occasional observations in the Mitaraka survey database .

In conclusion, the following major animal taxa were surveyed: Actinopterygii, Amphibia, Annelida, Arachnida, Insecta and Squammata.

Résumé :

L’expédition naturaliste Mitaraka "La Planète Revisitée Guyane 2015" a eu lieu dans le sud de la Guyane organisée en février-mars et en août 2015. Elle a permis à plus de cinquante scientifiques d’inventorier les groupes suivants : Actinopterygii, Amphibia, Annelida, Arachnida, Insecta, Mollusca et Squamata, avec un effort particulier sur les Ordres à la fois riches et méconnus, comme les Coléoptères, Diptères, Hémiptères et Hyménoptères. La zone forestière étudiée présente un relief de collines et inselbergs, avec une grande variété de milieux. Les objectifs principaux étaient de découvrir de nouvelles espèc es pour la science, de signaler de nouvelles espèces pour la Guyane et de dresser un inventaire de référence pour les études de biogéographie. L’organisation de la mission et les phases post-terrain s’appuient sur des coordinateurs par grands groupes taxinomiques. L’effort de collecte, en quantité et en diversité de méthodes, est certainement le plus important jamais déployé en Guyane sur une courte période. Treize types de pièges différents ont été utilisés : 4 types de pièges d’interception et 9 types de pièges fondés sur l’attraction. Des méthodes de recherche active (13 techniques) et d’extraction à partir du substrat (5 techniques, dont tamis Winkler, mise en émergence de bois mort, etc.) ont complété l’échantillonnage. Le processus de traitement des échantillons est décrit en montrant la différence entre les collectes actives et le processus plus long et complexe de traitement des échantillons des pièges massifs comme les pièges vitres, les Malaise, les assiettes colorées et les pièges lumineux automatiques. Après une phase de tri qui a duré moins d’un an pour la plupart des groupes, un réseau de 165 taxonomistes a été mobilisé par les coordinateurs pour l’étude des échantillons. Les données sont gérées dans une base de données d’observation et dans la base de données des collections du Muséum national d’Histoire naturelle (Paris). Elles sont largement diffusées, notamment en France via l’INPN (Inventaire national du Patrimoine naturel) et au niveau international par le GBIF (Global biodiversity information facility).

Résultats-Valorisation :

A la date de mai 2018, les organisateurs ont recensé :

• 44 articles publiés mentionnant du matériel de l'expédition
• 66 espèces nouvelles pour la Science;
• 29 premiers signalements pour la Guyane.

Un thématique de la revue Zoosystema est en cours de préparation.