Going up! - Jewel beetles (Coleoptera : Buprestidae ) along an altitudinal transect in Costa Rica.
along an altitudinal transect in Costa Rica
Abstract: After an extensive 9–year survey of the Organization for Tropical Studies’ La Selva Biological Station (50-150 m elevation), the arthropods of La Selva (ALAS) project extended its sampling over a 2000m altitudinal transect on the slopes of Volcan Barva. Standardized samples have been taken at 300, 500, 1100, 1500 and 2000 m during the dry seasons of the past 5 years. A total of 249 species in 20 genera have been collected at La Selva (219 and 20) and on the transect (59 and 12). In general, species richness declined with altitude. Small leaf-miners predominated in all faunas and were the only forms sampled at elevations above 1000m. Although sample sizes are small, middle and high elevation sites appear to have faunas distinct from the lowlands and each other. At middle elevations the genus Neotrachys, whose hosts are ferns, was prominent. Even in this relatively well-studied family, 66%of the species sampled are undescribed.
The Buprestidae do not show a peak of diversity at middle elevations. The two sites below 1000 m both recorded more than 20 species of buprestids, whereas those above 1000 m each yielded fewer than 10 species. Although it has been sampled more intensely, La Selva has many more species of buprestids; however, further analysis taking sampling intensity into account is needed to determine the significance of this difference
The elevation of 1000 m also seems to a break-point in buprestid distributions ecologically: Of the 47 species found below 1000 m, 13 were borers (28%), whereas all 16 of those sampled above 1000 m were leaf-miners.
Although sample sizes are small, middle and high elevation sites appeared to have faunas distinct from the lowlands and each other.
Of the leaf-mining genera at La Selva and on the transect, Lius and Neotrachys seem to be mid-elevation specialists, whereas the large genus Hylaeogena (26 species at La Selva) is conspicuously absent (Hespenheide, in preparation).
In all, of the 30 species collected only on the transect 21 (70%) appear to be undescribed.
For 9 years the arthropods of La Selva (ALAS) project surveyed a number of focal taxa of arthropods at the Organization for Tropical Studies’ La Selva Biological Station (50-150 m elevation) to determine the effectiveness of a variety of sampling methods in estimating the diversity of these taxa in a tropical wet forest (Longino & Colwell, 1997; Longino et al., 2002). For the past 5 years the ALAS project has extended its sampling over a 2000m altitudinal transect on the slopes of Volcan Barva to investigate patterns of diversity with elevation. In some studies middle elevations have been observed to have larger faunas compared to both higher and lower elevations (Janzen et al. 1976) which may be an artifact of what has been termed the “mid-domain effect” (Colwell et al., 2005 and included references). Other studies have not found a mid-elevation peak (Wolda 1987, McCoy 1990), so ALAS has taken standardized samples at 300, 500, 1100, 1500 and 2000 m on Volcan Barva during the dry seasons of the past 5 years to (a) determine whether such a peak exists and (b) test whether it is due to the mid-domain effect.
Dr. Henry A. Hespenheide
Department of Ecology and Evolutionary Biology
University of California
Los Angeles, CA 90095-1606
Neotrachys on the Barva transect
In the period since my revision of Central American Neotrachys (Hespenheide 1982), continued collecting has yielded a number of specimens for study, primarily from mid- to high elevation sites. Hosts of the genus are tree ferns or members of the fern vine genus Gleichenia. Neotrachys occurs at La Selva, was sampled at all sites on the on the Barva transect except the 1500 m site, and has the greatest diversity (4 species) at the 1100 m site. [Figure] The ALAS altitudinal transect has yielded specimens of what have proven to be three undescribed species of Neotrachys (Hespenheide, in preparation).
Samples by all methods at the five transect sites have yielded 59 species in 12 genera, of which 47 species in 11 genera were found in Malaise samples. The following table summarizes all collections at all sites by ecology and genus:
Baseline: the Buprestidae of La Selva
A total of 219 species in 20 genera have been collected at La Selva by hand collecting, rearing, and the ALAS project. The fauna is dominated by 157 species of leaf-miners (72%) in 7 genera. Of the 132 species sampled by ALAS, Malaise trapping was the most effective sampling method, capturing 88% of all individuals and 75% of the species. Sampling significantly increased the fauna known from hand collecting and rearing by 47 additional species. Of all species, many (64, 29%) are represented by single specimens, and 64% of the species are undescribed. Canopy fogging yielded 20 species not collected other ways, but only a few woody species were fogged and usually at times of the year when buprestids were less active (as determined by Malaise trapping).
LS Transect All
elevation (m): - 0300 0500 1100 1500 2000 sites
borers -misc large 18 2 6 - - - 21
Paragrilus 3 - - - - - 3
Agrilus 34 3 3 - - - 37
Callimicra 10 1 1 - - - 11
total 65 6 10 0 0 0 72
miners -Brachys32 5 6 - 1 1 34
Taphrocerus 12 5 5 - - - 13
Lius 6 - 1 3 - - 9
Leiopleura 38 8 4 - 1 - 43
Pachyschelus 38 2 5 2 2 1 45
Hylaeogena 26 - - - - - 26
Neotrachys 2 2 2 4 - 1 7
total 154 22 23 9 4 3 177
TOTAL 219 28 33 9 4 3` 249
Sampling on the Barva transect
The ALAS project used seven kinds of sampling at each of the five sites on the Barva transect, but - as at La Selva - Malaise trapping was the most effective method of collecting buprestids. At each site at total of 100 Malaise samples were taken from 20 traps (vs. 742 samples from 19 traps at La Selva). Although a few samples from the 1500 m site remain to be prepared, the following results can be presented:
Representative Neotrachys from the Barva transect: N. resplendens, N. concinna,N. n.sp. nr estebana.
For the Buprestidae sampled on an elevational transect on Volcan Barva, Costa Rica:
v59 species in 12 genera were sampled;
vdiversity is highest at La Selva and decreases with increasing elevation, so there is no mid-elevation peak in diversity;
vonly leaf-miners were sampled above 1000 m;
vmiddle and high elevation sites appeared to have faunas distinct from the lowlands and each other;
vthe genus Neotrachys is an example.
A symposium will be proposed for next year’s ESA meeting to present a more extensive report of ALAS transect data.
Field Sites :
Volcan Barva Transect -
Cantarrana Refuge field site, 350 m, 2004
John T. Longino provided the photographs. C. Bellamy and S. Bílý determined specimens. The ALAS Project at La Selva and the Barva transect has been funded by National Science Foundation grants BSR 9025024, DEB 9401069, DEB 9706976, and DEB-0072702 and the National Geographic Society. Additionally, I have been supported by grants from the UCLA Academic Senate and by departmental and personal funds.
El Ceibo station field site, 500 m , 2003
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effect: there's a baby in the bathwater. American Naturalist.
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Biological Journal of the Linnnean Society, London. 30: 313-323.
1170 m Refuge field site, 2001
Finca Murillo field site, 1500 m 2005
Refugio Vara Blanca field site, 2000 m, 2002