A Preliminary Inventory of the Platynini (Coleoptera: Carabidae)
of Ranomafana National Park, Madagascar

Emily S. Elsom1,2 and David H. Kavanaugh1

1 California Academy of Sciences, Department of Entomology, Golden Gate Park, San Francisco, CA 94118
2 San Francisco State University, Department of Biology, 1600 Holloway Ave., San Francisco, CA 94132

 

ABSTRACT
     In countries like Madagascar, where biological diversity is high but also highly threatened, it is imperative that we gather a baseline of information on little known taxa. This information will have broad application for future work in systematics and conservation. For this research, the tribe Platynini was chosen because it is the most diverse and abundant of the ground beetle tribes represented in Ranomafana National Park (RNP). Work with previously collected specimens, and a collecting expedition to RNP, have identified at least 56 morphospecies in 10 different genera. Almost all of these are new locality records for RNP, including at least 18 undescribed species. A species list for RNP, with all species compared to type specimens, will be created. Microhabitat and collecting method information, known distributions for each species within RNP and across Madagascar, and a key to the species of RNP (both online and in standard form) will be included in this research. We also discuss the apparent seasonality of the carabid fauna at RNP, the difficulty and inappropriateness of standard mass collecting techniques and quantitative sampling for carabids in tropical areas, and the need for collaboration with local Malagasy people in order to conduct a thorough inventory for this or any group.

 

INTRODUCTION
     The tribe Platynini was chosen because it is diverse, abundant, and understudied. Platynines are a common and easily recognizable tribe of ground beetles (Family Carabidae) found worldwide. The known Malagasy platynine fauna is extremely rich, but remains relatively unknown in some areas. In Ranomafana National Park (RNP), for example, only five species of Platynini have been previously recorded (Basilewsky 1985).

     In addition, this group may prove useful as an indicator taxon for monitoring the biodiversity of RNP, but much more study is needed to determine if this is feasible. The current research provides a baseline of information by identifying which species are present in the Park. The field work also provided insight into a possible sampling regime to aid in the long-term monitoring of the RNP's habitats.

     My research will test the hypothesis that the platynine fauna of RNP is much more diverse than previously recorded, and that the lack of previous records from the area is due to a lack of collecting.
Another goal was to test whether sampling in a systematic, quantitative way could appropriately document the faunal diversity.


RESEARCH OBJECTIVES

  • Gain expertise in the identification of Madagascar platynines and learn as much as possible about their distribution and habitat requirements;
  • Design and implement a biotic inventory, including a sampling regime, that balances easy implementation with an opportunity to encounter maximum diversity;
  • Produce valuable tools such as species lists, keys, and papers to contribute to the knowledge of this group and facilitate further inventory work at RNP, especially by local Malagasy biologists.

 

METHODS
FIELD METHODS and STUDY SITES
     All specimens examined were collected in Ranomafana National Park between 1988 and 2001. The 43,500 hectare area of RNP contains relatively undisturbed lowland rain forest and cloud forest at elevations between 400 and 1500 meters (Wright 1997). Within RNP five main areas were sampled. These are shown in Figure 1. We participated in a field expedition to RNP during January 2001. Twenty days were spent in the field collecting carabid beetles primarily by the following methods: beating live and suspended dead vegetation, scraping the bark of trees, searching in suspended masses of organic debris, and searching at night. Mass sampling techniques, including pitfall traps, malaise flight traps, and UV and mercury vapor light traps, were also used. All specimens were killed with ethyl acetate fumes and later preserved in 70% ethanol.


SPECIES IDENTIFICATION
     The beetles were sorted to morphospecies and identified using existing keys (Basilewsky 1985, Jeannel 1948). To confirm these identifications, we compared specimens to the holotypes or homotypes of all 324 known Malagasy platynines at the Museum National d'Histoire Naturelle in Paris.
Lower Vohiparara
Talatakely
Vohiparara Village
Upper Vohiparara
Figure 1. Ranomafana National Park: Locator Map and Map of Collecting Localities. Photographs show the typical habitat of each locality.
PRELIMINARY RESULTS
TAXONOMY
     We have identified 56 species of Platynini from 10 different genera. Under the existing classification, the
following genera (with numbers of species in each) are represented at RNP: Euleptus (1), Liagonum (7),
Megalonychus (3), Neobatenus (1), Epicolpodes (1), Lobocolpodes (1), Haplocolpodes (1),
Notocolpodes (3), Neocolpodes (34), and Catacolpodes (4). This represents an expected jump in the
number of species recorded from RNP. Of the five species previously recorded, we definitively identified
only three (N. gemmula, N. parenthesis, and H. perrieri). The other two species (N. tetragonus and
N. micaauri) are potentially present in our samples, but further dissection is needed to be certain. After
comparing the material to type specimens, it was determined that at least 18 new species (most in the genus
Neocolpodes) have been collected.

Figure 2. Two new species of Neocolpodes (1 & 2) with details of the elytral apex shown for each.
Neocolpodes porphyreticus (3) and Notocolpodes gallienii (4) are shown to the right.

 

     Figure 2 (1&2) shows two new species of Neocolpodes discovered in RNP. The species are very similar except for the shape of the elytral apex and male genitalia. This is typical for the Platynini of Madagascar and represents a challenge which must be overcome in order to create a user-friendly identification key. Figure 2 (3 & 4) also shows two extremely similar species that are currently placed in different genera, based principally on chaetotaxic differences. The use of these differences for higher classification is questionable, but the characters remain useful for species identification. Our key will employ the following useful characters (Figures 3-6).
In the first few couplets of the forthcoming identification key, species will be
broken into three categories (labelled at left) based on their elytral apices.
Figure 3. Elytral apex. Neocolpodes eucharis, Notocolpodes hylonomus, Neocolpodes dialithus (l to r).
Figure 4. Elytral microsculpture.
     Microsculpture can be classified as strongly isodiametric (1. Neocolpodes eucharis), slightly transverse
(2. Notocolpodes hylonomus), moderately transverse (3. Neocolpodes dialithus), strongly transverse,
forming horizontal lines with few or no closed cells (4. Neocolpodes new sp.) or effaced (5. Neocolpodes
imerinae).
Several species have asymmetrical lobes on the fourth metatarsomere (2) while others, including all Neocolpodes, have symmetrical lobes (1). Another useful tarsal character is the presence (3) or absence (4) of setae on the ventral side of the fifth metatarsomere.
Figure 5. Tarsi.
These two species, Neocolpodes gemmula (left) and Liagonum
vadoni (right) show the extremes of narrow and extremely wide
lateral explanations, respectively.
Figure 6. Lateral explanation of the pronotum.


ECOLOGY / CONSERVATION IMPLICATIONS
     While admittedly not sampled with equal effort, the five study areas do show interesting preliminary differences in faunal composition (Table 1). Eighteen species were found in at least 3 of the 5 collecting localities, and six were found in fourof the five localities. These species can be considered generalists for the initial data evaluation period. Lobocolpodes murex (Figure 7) is an example of a generalist species. There are also 27 specialists so far found in only one area of RNP. An example is shown in Figure 8. Neocolpodes andriana is only found in Upper Vohiparara and is known from only two specimens collected in 1998.

Table 1. Faunal composition of collecting localities.
     The Vohiparara Village fauna represents the indicator potential of this group. This locality is the most
disturbed of the sites visited, composed of secondary flood plain adjacent to active rice paddies. The seven
species collected here are usually found in inhabited or disturbed areas in the central plateau of the country. If
these species were to show up in the interior of the protected region of RNP, it would indicate a possible
decline in habitat quality. For example, Megalonychus lebisi (Figure 9) is a species so far found only at the
Vohiparara Village site, newly discovered in RNP as a result of our 2001 field expedition, but otherwise
widespread through east and central Madagascar.
Figure 7. Lobocolpodes murex                       Figure 8. Neocolpodes andriana                    Figure 9. Megalonychus lebisi
DISCUSSION
     During our field work in January, we discovered a microhabitat previously overlooked in carabid collecting
efforts. Large masses of forest litter, termed "humidity lenses" by Erwin (1979), likely serve as refuges for
carabid beetles during the dry season. Most platynines found during January 2001 (the very start of the rainy
season) were in these masses. In April 1998 (the middle of the rainy season), these same species were found
mostly in trees and much higher off the ground. We hypothesize that the beetles seek refuge in the humid
masses until freed to move higher into the trees as the rainy season progresses. These anecdotal data allude to
a seasonal movement of platynines based on rainfall patterns. Only by following their movement year round will
this pattern be confirmed, and this can only be done in collaboration with local Malagasy people.

     The other main point of discussion is the inadequacy of traditional sampling methods for collecting tropical
Carabidae. In the past, most sampling for this taxon has been done with pitfall traps (Venilla & Rajagopal 1999).
This method not only misses almost all of the arboreal fauna, but also fails to reveal the true habitats of the
beetles. The nocturnal beetles most likely fall into the traps at night while in transit. For future assessments of
carabid biodiversity, a daytime sampling regime with a high probability of locating their clustered, arboreal
resting-places is sorely needed. This type of searching technique, focused on carefully selected potential
microhabitats, yields poor quantitative data for statistical analysis, but the need to find the maximum number of
species must also be considered. For any random, quantitative sampling unit devised, the real danger in areas
like RNP is an extremely large proportion of zeroes in the sampling data. Further research and thought are
needed in order to attempt a resolution to this ever-present problem for tropical entomologists.



LITERATURE CITED
Basilewsky, P. 1985. Insectes Coleopteres, Carabidae Platyninae, in Faune de Madagascar. 64: 1-543.

Erwin, T.L. 1979. Thoughts on the evolutionary history of ground beetles: Hypotheses generated from comparative faunal analyses of    lowland forest sites in temperate and tropical regions, 539-594. In Carabid beetles: Their evolution, natural history, and    classification. T.L. Erwin, G.E. Ball, D.R. Whitehead Eds. Dr. W. Junk: The Hague.

Jeannel, R. 1948. Coleopteres Carabiques de la region Malgache (Deuxieme partie), in Faune de l'Empire francais. 10: 373-766.

Vennila, S. and Rajagopal, D. 1999. Optimum sampling effort for study of tropical ground beetles (Carabidae: Coleoptera) using pitfall    traps. Current science. 77: 281-283.

Wright, P. 1997. The Future of Biodiversity in Madagascar, 381-405. In Natural Change and Human Impact in Madagascar,    Goodman, S.M. and Patterson, B.D. Eds. Smithsonian Institution Press: Washington D.C.
ACKNOWLEDGEMENTS
     Funding for this research was provided by the CAS Research Division and the SFSU College of Science and Engineering. We
would like to thank the CAS Department of Entomology for support, facilities, and use of the collection. Additional specimens were
provided by the U.S. National Museum and Montana State University. Many thanks to the members of the 4th Madagascar
expedition- Roberta Brett, Kathryn Kavanaugh, Flor Vargas, Dr. Kip Will, and our Malagasy colleagues. The staff of ICTE/MICET in
Antananarivo were invaluable, as were the staff of RNP, and our friends Balsama, Helian, et al. Dr. Thierry Deuve gave us access to
type specimens and was an extremely generous host at the MNHN in Paris.
To read more about the California Academy of Sciences expeditions to Madagascar, click here.