The presence-absence situation and its impact on the assemblage structure and interspecific relations of Pronophilina butterflies in the Venezuelan Andes (Lepidoptera: Nymphalidae)

Abstract

Assemblage structure and altitudinal patterns of Pronophilina, a species-rich group of Andean butterflies, are compared in El Baho and Monte Zerpa, two closely situated and ecologically similar Andean localities. Their faunas differ only by the absence of Pedaliodes ornata Grose-Smith in El Baho. There are, however, important structural differences between the two Pronophilina assemblages. Whereas there are five co-dominant species in Monte Zerpa, including P. ornata, Pedaliodes minabilis Pyrcz is the only dominant with more than half of all the individuals in the sample in El Baho. The absence of P. ornata in El Baho is investigated from historical, geographic, and ecological perspectives exploring the factors responsible for its possible extinction including climate change, mass dying out of host plants, and competitive exclusion. Although competitive exclusion between P. ornata and P. minabilis is a plausible mechanism, considered that their ecological niches overlap, which suggests a limiting influence on each other's populations, the object of competition was not identified, and the reason of the absence of P. ornata in El Baho could not be established. The role of spatial interference related to imperfect sexual behavioral isolation is evaluated in maintaining the parapatric altitudinal distributions of three pairs of phenotypically similar and related species of Pedaliodes, Corades, and Lymanopoda.

Fig 1

Study sites and distribution of Pedaliodes ornata in the Cordillera de Mérida (1: Pedaliodes ornata ornata; 2: Pedaliodes ornata haroldboxi; black area: land above 3,000 m asl, dark grey area: land above 2,000 m asl).

Fig 2

Male adults of Pedaliodes ornata, Pedaliodes minabilis, and Pedaliodes montagna. 1. Pedaliodes ornata haroldboxi, Pico Tonojo, 2. Pedaliodes ornata ornata, Monte Zerpa, 3. Pedaliodes minabilis, Monte Zerpa, 4. Pedaliodes minabilis, El Baho (form luteocosta), 5. Pedaliodes montagna, Monte Zerpa, 6. Pedaliodes montagna, El Baho.

Fig 3

Altitudinal distribution patterns of three pairs of parapatric species in Monte Zerpa (MZ) and El Baho (EB). Box and whiskers plot with median, lower, and upper quartile, minimum and maximum and outside values of altitude range.