Cicindela galapagoensis

A tiger beetle is hardly the first organism that comes to mind when the Galapagos Islands are mentioned. However, the Islands are home to a single endemic member of this subfamily, Cicindela galapagoensis.

Cicindela galapagoensis was first collected by then Stanford student F. X. Williams while he was serving as an entomologist on the California Academy of Sciences 1905-1906 expedition to the Galapagos. It was over ten years until this species was formally described, though this distinction went to German entomologist Walther Horn. In Coleoptera of the Galapagos Islands E.C. Van Dyke curtly mentions: “A tiger beetle collected by Williams was described by Dr. Walther Horn … as Cicindela galapagoensis. It had been submitted to him for his opinion.”

This species is represented by two color forms: a dark and a pale form. As one might suspect, this variation has led to some taxonomic confusion. The dark form of C. galapagoensis was described under the name Cicindela vonhageni in 1938, by American Museum of Natural History curator A.J. Mutchler, from 7 specimens collected by W. von Hagen. Additionally, a subspecies, C. galapagoensis discolorata, was described in 1967 from a single specimen collected on Genovesa Island. However, in 1976, Hans Reichardt synonymized vonhageni and galapagoensis discolorata with galapagoensis after finding evidence for only a single species based on the presence of intermediate forms in a large series of specimens.

Cicindela galapagoensis has been collected from seven major islands¹ where it inhabits sand beaches, mud flats, and salt tidal marshes. The adults have been collected at night with no reported observations of activity in the daytime. The larvae have been described and are found in similar habitats to the adults.

While C. galapagoensis is the sole endemic species of tiger beetle in the archipelago, a mainland species, Cicindela trifasciata was apparently introduced onto Santa Cruz Island and subsequently spread to several sites on during an extreme El Niño event in 1982-1983.  Since the apparent introduction, the trifasciata populations have grown to vastly out number the endemic speceis on the order of hundreds to one. As expected, the number of galapagoensis observed in recent studies has dramatically dropped at the sites where the two species co-occur, almost certainly due to fierce competition for prey and potentially larval habitat.

In addition, Cassola et al. noted that C. galapagoensis was not observed on Genovesa Island and, most distressingly, reported that the species primary habitat on the island, a small sand beach, had been incorporated into the tourist trail. The resultant trampling likely wiped out any larvae and rendered the habitat unsuitable, resulting in the extinction of this population.

Back in January, I have the privilege to spend ten days in the Galapagos. Though I did not see any tiger beetles, one of our stops was the beach at Genovesa, on Darwin Bay. We went ashore just after the equatorial sun rose and I was struck by the traces of human activity. Old graffiti was conspicuously emblazoned on the cliffs and footprints were almost everywhere across the small beach. As we proceeded down the beach the impact of foot traffic became even more apparent.

But, as a whole, Cicindela galapagoensis is not in danger. The Santa Cruz and Genovesa populations are not the rule and most of the species habitat is free from introduced competitors and the menace of human foot traffic. Adequate surveys are needed to assess the extent of tricfasciata colonization and the overall health of C. galapagoensis populations in order to develop management strategies. Ultimately, with careful management, this enigmatic species can continue to thrive.

Notes:

¹ Fernandina, Floreana, Genovesa, Isabela, Marchena, San Cristóbal, and Santa Cruz (Peck 2006)

References:

Cassola, F., Roque-Albelo, L., and Desender, K. 2000. Is the Galápagos endemic tiger beetle threatened with extinction? Noticias de Galápagos no. 61: 23–25.

Horn, W. 1915. Coleoptera, Fam. Carabidae, Subfam. Cicindelinae. In P. Wytsman, ed., Genera Insectorum, 82C: 209-487, pl. 16-23.

Mutchler, A.J. 1938. Coleoptera from the Galápagos Islands. American Museum Novitates 981: 1-19.

Van Dyke, E.e. 1953. The Coleoptera of the Galápagos Islands. Occasional Papers of the California Academy of Sciences 22: 1-181.

One response

  1. Too bad you couldn’t manage a side trip to one of the other islands where C. galapagoensis still occurs.

    February 18, 2012 at 11:38 am

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