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1 December 2016 Orchid Bees (Hymenoptera: Apidae: Euglossini) of Cusuco National Park, State of Cortés, Honduras
Kenneth W. McCravy, Joseph Van Dyke, Thomas J. Creedy, David W. Roubik
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Abstract

Orchid bees (Hymenoptera: Apidae: Euglossini) are abundant and important pollinators of Neotropical forests, but orchid bee diversity is still poorly known in much of Mesoamerica, particularly in cloud forests. This paper presents results of a 2012 to 2013 survey of orchid bee diversity in Cusuco National Park, a cloud forest environment in northwest Honduras. Orchid bees were collected using insect nets at bait stations with chemical attractants. Bait stations were located at 68 sample sites throughout the park. We collected 4,293 orchid bees representing 24 species and 4 genera. One species, Euglossa imperialis Cockerell, accounted for 67.6% of the total individuals collected. A substantial easterly range extension was established for Eufriesea pallida (Kimsey). Our study provides the first intensive inventory of cloud forest orchid bee diversity in the region. Furthermore, it provides baseline data for future studies of orchid bees in a key biodiversity area that is threatened by human population growth and associated land use changes.

Orchid bees (Hymenoptera: Apidae: Euglossini) are ubiquitous and important pollinators that can comprise up to 25% of Neotropical forest bee communities (Roubik & Hanson 2004). There are over 200 known species of orchid bees, and the tribe ranges from Mexico to Argentina (Roubik & Hanson 2004; Nemésio & Silveira 2007) as well as southern North America (Minckley & Reyes 1996; Skov & Wiley 2005; Pemberton & Wheeler 2006; Eltz et al. 2011). However, knowledge of orchid bee diversity varies greatly with location. In Mesoamerica, for instance, Ramírez et al. (2002), in their catalog of Neotropical orchid bee species, list about 69 species records for Panama, but only about 10 for Honduras. A more recently published catalog of bee species and their geographic ranges published by Moure et al. (2012) lists about 66 orchid bee species records for Panama, but only about 20 for Honduras. This latter number is undoubtedly a function of the dearth of orchid bee studies in Honduras. Ascher & Pickering's (2015) Discover Life database has 29 species listed for Honduras, although this may be less accurate due to the broad and under-verified source data used by this resource.

Much of their ecological importance stems from the behavior of male orchid bees, which are among the few pollinators that visit flowers to collect aromatic compounds or associated chemicals (Roubik & Hanson 2004). These fragrances appear to be associated with species recognition, competition, and mate choice (Zimmermann et al. 2009). Orchid bees are best known for their associations with orchids, and are important pollinators of roughly 650 species in this plant family. However, they are associated with many other plant species as well, spanning about 30 families (Dressler 1982; Ackerman 1983; Roubik & Hanson 2004; Ackerman & Roubik 2012). Gilbert (1980) cited orchid bees as particularly important Neotropical “link organisms,” stating that “a single euglossine species may link plant species from all stages and strata of a forest into a system of indirect mutualism.”

Mesoamerica is one of the world's biodiversity hotspots (Mittermeier et al. 1999). Cusuco National Park, containing primarily high elevation cloud forest in northwest Honduras, is a site of critical conservation concern based on its vertebrate fauna (Le Saout et al. 2013), but little is known of the invertebrate diversity within the park. Cusuco National Park has been designated a Key Biodiversity Area, but is threatened by human population growth and associated land cover changes driven by practices such as conversion of forests to coffee plantations (Green et al. 2012). To expand our knowledge of the orchid bee fauna of Honduras, and to provide baseline data on orchid bee diversity in a location of concern that is undergoing rapidly changing land use patterns, we conducted a survey of the orchid bees of Cusuco National Park.

Materials and Methods

STUDY LOCATION

The study was done from mid-Jun to early Aug in 2012 and 2013 at Cusuco National Park, about 30 km west of San Pedro Sula in the State of Cortés, in northwest Honduras (Fig. 1a). Cusuco National Park is an area of about 23,400 ha and ranges in elevation from just above sea level to 2,425 m. Habitat types include disturbed and undisturbed mature broadleaf forest, secondary broadleaf forest, disturbed pine-broadleaf forest, mature pine forest, open disturbed grassland, open disturbed logged areas, and open coffee plantations. Monthly mean rainfall for all sample sites ranged from 60.8 mm in Mar to 252.4 mm in Jun, with mean total annual rainfall of 1,786.0 mm. Mean total annual rainfall by habitat type ranged from 1,743.0 mm for disturbed broadleaf forest (Mar minimum = 60.9 mm, Jun maximum = 245.8 mm) to 1,835.5 mm for secondary broadleaf forest (Mar minimum = 61.8 mm, Jun maximum = 258.3 mm). Mean precipitation for each sample site was extracted from downsampled WorldClim data ( www.worldclim.org) interpolated from weather station data in San Pedro Sula.

SAMPLING OF ORCHID BEES

Orchid bees were collected with insect nets at bait stations, which consisted of a cotton ball with a chemical attractant suspended about 1.7 m above the ground by a string. Five bait stations, about 5 m apart, were established during each collection period. Five chemical attractants were used (benzyl acetate,