Presence of Vaejovis franckei in epiphytic bromeliads in three temperate forest types.
Reports of scorpions on epiphytic bromeliads in temperate forests
are scarce. Here we present some ecological aspects of this animal-plant
interaction in three different types of temperate forests (pine,
pine-oak and oak forest) in Oaxaca, Mexico. From 2005 to 2007, we
collected 373 bromeliads belonging to 10 species, and each plant was
defoliated in search of scorpions. We found 35 individuals of Vaejovis
franckei Sissom 1989 in 19 bromeliads: 22 specimens in Tillandsia
carlos-hankii with 21% occupancy and an average abundance of 2.1 [+ or
-] 1.9 individuals/plant; 12 specimens in T. prodigiosa (10% occupancy,
average abundance = 1.6 [+ or -] 0.6) and one specimen in T. calothyrsus
(3% occupancy, average abundance = 1 [+ or -] 0.0). Pine-oak forest had
29 individuals; pine forest, 4 individuals; and oak forest, 2
individuals. Percentage of occupancy differed among localities, while
average abundance remained the same. Vaejovis franckei preferred T.
carloshankii and pine-oak forest, which was correlated with the
percentage of occupancy but not with the average abundance.
Keywords: Phytotelmata, Mexico
Forests and forestry (Mexico)
Forests and forestry (Environmental aspects)
Scorpions (Environmental aspects)
Ruiz, Gabriel Isaias Cruz
|Publication:||Name: Journal of Arachnology Publisher: American Arachnological Society Audience: Academic Format: Magazine/Journal Subject: Biological sciences; Zoology and wildlife conservation Copyright: COPYRIGHT 2009 American Arachnological Society ISSN: 0161-8202|
|Issue:||Date: Sept, 2009 Source Volume: 37 Source Issue: 3|
|Product:||Product Code: 7949100 Forests & Parks NAICS Code: 71219 Nature Parks and Other Similar Institutions|
|Geographic:||Geographic Scope: Mexico Geographic Code: 1MEX Mexico|
The presence of scorpions in tank-type bromeliads has been widely
reported (Lucas 1975; Richardson 1999; Santos et al. 2006); however,
most studies of scorpions on bromeliads have taken place in tropical
forests, whereas research on bromeliads in temperate forests is scarce
(Lucas 1975; Ochoa et al. 1993; Sissom 2000).
The present study sought to evaluate different ecological aspects of scorpions living in tank-bromeliads in three types of temperate forests. The study was carried out in Santa Catarina Ixtepeji in the state of Oaxaca, Mexico, located at 17[degrees]09'-17[degrees]11'N and 96[degrees]36'-96[degrees]39'W. Its climate varies with the altitude, and ranges from temperate to cold sub-humid with summer rains. The mean annual temperature and precipitation are 14[degrees] C and 1000 mm, respectively (INEGI 1998). Three sampling sites were selected: Pena Prieta (2870 m), a pine forest; La Petenera (2547 m), a pine-oak forest; and El Cerezal (2300 m), an oak forest. From 2005 to 2007, we sampled 373 bromeliads belonging to ten species. Bromeliads were transported to the laboratory where each plant was defoliated, and each leaf was carefully inspected. Scorpion specimens were preserved in 70% alcohol. We used the taxonomic keys of Hoffmann (1931) and Stockwell (1992) to identify the scorpions. Collected specimens have been placed in the Coleccion Nacional de Aracnidos in the Instituto de Biologia (IB-UNAM) in Mexico City.
A total of 35 Vaejovis franckei Sissom 1989 was found in 19 of the 373 sampled bromeliads. We only found scorpions on Tillandsia prodigiosa (Lem) Baker 1889, Tillandsia carlos-hankii Matuda 1973 and Tillandsia calothyrsus Mez 1896. No specimens were found in Viridantha plumosa (Baker) Espejo 2002 (n = 22), Catopsis berteroniana (Schult. & Schult.f.) Mez 1896 (n = 17), Tillandsia macdougallii L.B. Smith 1949 (n = 39), T. oaxacana L.B. Smith 1949 (n = 50), T. magnusiana Wittm. 1901 (n = 10), T. bourgaei Baker 1887 (n = 30), or T. violaceae Baker, 1887 (n = 38).
The greatest number of scorpions was found in T. carlos-hankii (24 individuals), followed by T. prodigiosa (10 individuals) and T. calothyrsus (1 individual) (see Table 1). The percentage of occupancy differed among species ([Xsup.2.sub.2] = 7.60, P = 0.022, n = 167), whereas the average abundance of scorpions per plant was the same (T. prodigiosa = 1.6 [+ or -] 0.6, T. carlos-hankii = 2.1 [+ or -] 1.9 and T. calothyrsus = 1.0, ANOVA, [F.sub.2,17] = 1.03, P = 0.3).
Pine-oak forest (La Petenera) produced the greatest abundance of V. franckei, with 29 individuals, followed by pine forest (Pena Prieta) with 4 individuals and oak forest (El Cerezal) with 2 individuals. The percentage of occupancy differed among sampling localities (8% in Pena Prieta, 24% in Petenera and 3% in El Cerezal; [X.sup.2.sub.2] = 14.88, P = 0.006, n = 167), while the average abundance of scorpions per bromeliad did not differ significantly among sites (Pena Prieta = 1.3 [+ or -] 0.6, Petenera = 2.1 [+ or -] 1.3 and Cerezal 1.0; ANOVA, [F.sub.8,16] = 1.1, P = 0.4). The average abundance of scorpions by bromeliad (r = 0.18, P = 0.9) was not correlated with the size of the bromeliad, although the percentage of occupancy was significantly related to it (Kendall Tau = 0.154, P = 0.018, n = 107)
Most studies of arthropods living inside bromeliads do not show specificity for particular bromeliad species (Richardson 1999; Ospina-Bautista et al. 2004; Liria 2007), even though some arthropods show a strong preference for certain species of bromeliads (Quevedo & Vasconcellos-Neto 2005; Osses et al. 2007). In our case, V. franckei preferred T. carlos-hankii. This preference could be related to the architecture and/or color of the plant; e.g., T. carlos-hankii has green leaves with a purple base. In contrast, T. prodigiosa possesses green pale leaves. These differences could promote microclimatic conditions that favor the presence of scorpions, although further research is required to reach such a conclusion.
Although bromeliad size did not correlate with scorpion abundance, there may be a minimum size of bromeliad that can support scorpions, since scorpions were absent in three small species (V. plumosa, T. macdougallii and T. magnusiana) that do not form a water tank. Size limits the amount of water and leaf litter that accumulates inside these bromeliads, resulting in a decrease in arthropod species richness and abundance (Benzing et al. 2000), including many species that scorpions prey upon. Other studies have also shown that small bromeliads have lower abundance and species richness of arthropods that scorpions feed on, potentially resulting in lower scorpion abundances in these bromeliads (Ospina-Bautista et al. 2004; Franco 2008). Scorpions were not found in T. oaxacana either, probably because of the plant's small size (17-30 cm in height) and its small tank, which retains a maximum of 300 ml of water, compared to 1400 ml for T. carlos-hankii (Franco 2008). Bromeliad size might also directly limit the presence of scorpions, as these arthropods are relatively large, measuring up to 6 cm in length. Space within the bromeliads might thus be inadequate to provide a refuge for scorpions. Accordingly, we observed scorpions only on the larger bromeliad species (between 50 and 75 cm in height) such as T. prodigiosa, T. carlos-hankii and T. calothyrsus.
Scorpions show high specificity for certain environmental conditions (Hoffmann 1931; Lourenco & Sissom 2000; Florez 2001; Prendini 2001). Physical conditions in the pine-oak forest site are probably the most ideal for V. franckei, given that it was most common in this forest type (29 individuals). The low abundance of V. franckei in the pine forest may explain why this scorpion was not found in T. violaceae in this forest type, despite the plant's suitability for the establishment of scorpions. Nonetheless, at least one other species of scorpion, C. flavopictus, has been found in this plant species in a cloud forest in Chiapas (Lucas 1975).
Although tank-type bromeliads appear to be a very attractive habitat for scorpions because they represent a potential source of food and refuge, in this study they colonized only a small percentage of the bromeliad specimens (9%). This result agrees with observations by Santos et al. (2006), who also reported a low percentage of occupancy (13%) for Tityus neglectus Mello-Leitao in four tank-type bromeliad species. Such low occupancy levels may be due to overall low scorpion densities, as reported across most types of vegetation (Bradley & Brody 1984).
This project was supported by SEP-CONACYT: SEP-2004-C01-48316. We thank Megan Lore and Sheeva Sreenivasan for help with the English in this paper.
Manuscript received 10 October 2008, revised 5 February 2009.
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Demetria Mondragon and Gabriel Isaias Cruz Ruiz: Centro Interdisciplinario de Investigation para el Desarrollo Integral Regional (CIIDIR) Unidad Oaxaca, Calle Hornos No. 1003. Santa Cruz Xoxocotlan, Oaxaca, Mexico. E-mail: email@example.com
Table 1.--Presence of Vaejovis franckei Sissom 1989 on different bromeliad species in three temperate forests in Santa Catarina Ixtepeji. a = number of sample plants, b = number of plants with scorpions, c = scorpion abundance. Bromeliad species Pine forest a b c Tillandsia prodigiosa (Lem) Baker, 1889 0 0 0 Tillandsia carlos-hankii Matuda, 1973 40 3 4 Tillandsia calothyrsus Mez, 1896 0 0 0 Bromeliad species Pine-oak a b c Tillandsia prodigiosa (Lem) Baker, 1889 40 5 9 Tillandsia carlos-hankii Matuda, 1973 18 9 20 Tillandsia calothyrsus Mez, 1896 0 0 0 Bromeliad species Oak a b c Tillandsia prodigiosa (Lem) Baker, 1889 37 1 1 Tillandsia carlos-hankii Matuda, 1973 0 0 0 Tillandsia calothyrsus Mez, 1896 32 1 1
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