Butterfly diversity in an Andene valley – Cosnipata (Kosñipata), Cuzco, S. Peru

by

Daniel Lacomme & Bruce Purser, Association des Lépidoptéristes de France

Butterfly species are related to an altitudinal gradient ranging from 500 to 3600 meters. Although the taxonomic list is not finalised, it is clear that species and sub-species of many genera change with temperature, humidity and vegetation, conditioned by the altitudinal gradient. The authors limit their summary to four genera – Morpho, Catasticta, Perisama and Pedaliodes.

The Cosnipata Valley, a tributary of the Madre de Dios, flows towards the NE and thus receives abundant humidity from the Amazon Basin. This humidity is reflected in the luxuriant vegetation which grades, almost without break, from lowland forest, through pre-montagne to high mountain « cloud forest », each biome having its particular butterfly and moth fauna. Virtually all collecting has been carried out along a gravel road which descends the valley. Study made at specific altitudes indicates important local variations in butterfly diversity which seem to be conditioned by local variations in humidity ; where the road crosses a major tributary, humidity is higher and butterflies more abundant, but where the road climbs steep slopes situated high above local streams, lower humidities coincide with markedly fewer butterflies. This tendency is confirmed by the relative abundance of butterflies along the banks of the Cosnipata, their original habitat prior to the construction of the nearby road.

The Genus Morpho (FABRICIUS, 1807) in the Cosnipata Valley

The genus Morpho (Nymphalidae) is one of the most interesting groups to relate to altitudinal distribution, ranging from the Amazonian plain to about 3000 m. Fourteen species occur in the Cosnipata Valley, including one endemic species and 5 endemic sub-species.

In addition to the close observation of the endemic M. absoloni and its exceptionally rare female (described in 1983), is the fact that there exists an altitudinal relay between species belonging to the same sub-genus. Thus, certain species of the same group are replaced by others, according to altitude :

M. telemachus – M. amphitryon (sub-genus Iphimedeia)

M. marcus – M. zephyritis – M. sulkowskyi (sub-genus Cytheritis)

M. absoloni – M. aurora (sub-genus Balakowskyna)

M. menelaus zischkai – M. godarti assarpai (via 2 or 3 successive forms), (sub-genus Grasseia)

Concerning M. godarti assarpai, a clear change in morphology affects the same sub-species ; convergent with M. menelaus on the Amazon plain, close to M. godarti didius at middle altitudes, it resembles M. godarti godarti towards 1500 m – its upper limit. This morphological variation relating to altitude, within a given species, remains to be confirmed and other equivalents should be established.

Photos of two living rare species have been made : M. cisseis and M. absoloni. Finally, the flight season at low altitude (200 – 1000 m) are grouped (May – July) while middle and high altitude species fly during the months of September to December.

The genus Catasticta, (Pieridae, BUTLER, 1870)

Among the many genera of pierid inhabiting the Cosnipata, we have observed 15 species of Catasticta. The authors are very grateful to Maurizio Bollino for his help in the identification of seven species. According M. Bollino, the area (from Acjanaco down along the road to Pillcopata) hosts no less than 28 species of Catasticta, including a recently described one (Catasticta pillcopata BOLLINO, 2008).

Ranging in altitude from 1200 to 2900 m, the genus attains maximum diversity (7 species) between 2000 and 2500 m where virtually all species are located near small creeks which cross the road (see photo) or along the banks of the Rio Cosnipata. The numerous waterfalls are frequented by Catasticta which fly in the spray and land on wet cliffs or close to running water. Their behaviour is reminiscent of certain species of the Indo-Australian genus Delias. There also exists a remarkable colour convergence between Catasticta and at least two other genera of pierid : Dismorphia niepelti and Leodonta chiriquensis, all three being parapatric between altitudes of 1500 and 2200 m.

Although there does not appear to be any significant altitudinal evolution in colour patterns, the majority of the black and white species, plus the Leodonta and Dismorphia occur below 2000 m, species above that altitude (notably C. collina & C. rileyi) tending to have dark grey dorsal patterns. The majority of species (10) were observed at precise altitudes while the remainder extended over an altitude of 200 to 400 m. The altitudinal distribution of individual species of Catasticta is remarkably limited.

The genus Perisama (Nymphalidae, DOUBLEDAY, 1847)

We have observed 10 species of Perisama in the Cosnipata Valley where maximum diversity occurs between 1500 and 1800 m i.e. slightly lower than Catasticta. Six species (alicia, philinus, comnena, hilara, jurinei & tristrigosa plus Diaethria alicia) were flying together at 1500 m, P. calamis fassli extending up to 3000 m where it was associated with Orophila cecidas, a genus which closely resembles Perisama. The following species have been observed :

Perisama frequents gravel roads and abandoned quarries and, although more abundant near the bottoms of humid valleys, is not directly associated with streams and waterfalls. Most species have an altitudinal range of about 1000 m but this seems to vary according to the season, several species (tringa, hilara & jurenei) being considerably lower (500m) in the dry season.

There appears to be a faunal change near 1800 m, several species (tringa, philinus, comnena, hilara, jurinei & tristrigosa) occuring below 1800 m, while P. calamis fassli, P. clisithera, P. moronina and Orophila cecidas occur above. This break may be related to the ancient limit of mountain forests (currently 3500 m) which were 1500 – 2000 m lower during the last Glaciation. The three species of Perisama found above 1800 m seem to be limited to southern Peru while those below 1800 m are widely distributed (N. Peru – Ecuador). This difference suggests that the three higher altitude species have had less time to colonise laterally and thus may have evolved more recently.

The genus Pedaliodes BUTLER, 1867 (Satyrinae)

The genus Pedaliodes is endemic to the Andes. Neotropical mountain Pedaliodes may be the most divers genus of butterflies, and is among the least well-studied. LAMAS (2004) lists 246 species of which 98 were described by PYRCZ et AL has recently described 14 species.

Pedaliodes are moderately-sized butterflies whose dorsal surfaces are generally uniformly brown in colour, only the ocelli and occasional patterns on the hind wings permitting field identification.

The Satyrinae, being essentially sedentary in habit, have evolved important phylogenic differentiation conditioned essentially by the deep and complicated valley system which characterises the eastern Andes.

Fifteen species of Pedaliodes (sensu stricto) have been identified in the Cosnipata Valley between about 1000 and the Acjanaco Pass (3650 m). Collecting has enabled the establishment of two or three altitudinal zones, with local overlap and sympatry, relating to vegetal discontinuities due to orientation of the valley and to local variations in humidity due to remoteness from humid, valley floors.

Among the 19 taxa comprising the following list, 4 are recently described while 3 are currently being defined.

Conclusion

The four genera – Morpho, Catasticta, Perisama & Pedaliodes – change with altitude, this species evolution being typical of many peri-Andene valleys. The considerable number of species which evolve with altitude are probably one of the major factors determining the overall diversity of lepidoptera within the eastern Andes.

A detailed description of the lepidoptera of the Cosnipata Valley will appear in a thematic number of Lépidoptères, the review of the ALF (Association des Lépidoptéristes de France), early 2011.