Trechus isabelae Borges & Serrano

Borges, Paulo A. V., Oromí, Pedro, Serrano, Artur R. M. & Amorim, Isabel R., 2007, Biodiversity patterns of cavernicolous ground-beetles and their conservation status in the Azores, with the description of a new species: Trechus isabelae n. sp. (Coleoptera: Carabidae: Trechinae), Zootaxa 1478, pp. 21-31 : 22-24

Trechus isabelae Borges & Serrano , new species

( Figs. 1–3 )

Type material: Holotype, male, Azores, São Jorge, Algar do Morro Pelado (= Algar do Montoso), 5– 11.VII.2004. (P.A.V. Borges & F. Pereira leg.). Paratypes 1 female, same locality as holotype, 7–11.V.2004 (P.A.V. Borges & F. Pereira leg.); 2 males and 1 female, same locality as holotype, 5–11.VII.2004 (P.A.V. Borges & F. Pereira leg.); The Holotype and two paratypes (1 male, 1 female) are deposited at the University of the Azores, Terceira (“Arruda Furtado” Collection); one paratype (female) is deposited at the Faculty of Sciences of the University of Lisbon, and the other one (male) at the University of La Laguna, Dep. of Animal Biology.

Additional material: One male was collected in the same locality (7–11.V.2004) for molecular analysis.

Etymology. The species is named after Isabel Amorim who has discovered several new species of Trechus in the Azores.

Diagnosis. Large species (4.8–5.38 mm) ( Fig. 1 ), dark brown pigmentation, with some lighter parts; appendages less pigmented (light brown), tibiae and tarsomeres with the same colour patterns as the femora; pronotum as dark as elytra. Eyes slightly convex; 3rd antennomere longer than 2nd; pronotum rather cordiform and transverse, with lateral furrows larger than in T. terrabravensis ; wingless.

Description. Length of holotype: 5.18 mm. Length of female specimens: 4.80–5.38 mm. Large size, convex and ovate. Head almost 1.30x as wide as long (females: 1.29–1.42), 0.78x narrower than pronotum (females: 0.74–0.78); eyes well-developed (0.025 mm), moderately convex, diameter of eyes as long as temples; temples with microchaetae. Frons slightly convex, the frontal furrows deeply curved and rounded. Anterior margin of labrum very concave. Maxillary palpi long and slender. Chaetotaxy: two pairs of supraocular setae; four setae in clypeus (outer ones larger); six setae on labrum, the outer ones being the largest. Antennae 2.99 mm long (females: 2.74–2.99 mm), reaching only the first quarter of elytra; the 3rd antennomere 1.32 x longer than 2nd (females, 1.11x–1.14x); 1st antennomere 2.0x longer than wide (females, 1.88x – 2.0x), 2nd antennomere 2.33x longer than wide (females: 2.60x – 2.67x), 6th–8th antennomeres 2.5x longer than wide (females: 2.67x – 3.0x), 9th–10th antennomeres 2.31x longer than wide (females: 2.14x – 2.8x), 11th antennomere 2.92x longer than wide (females: 2.86x – 3.6x). Pronotum convex, cordiform, highly transverse, 1.31x as broad as long (females: 1.30x–1.34x); side margins curved till hind angle; anterior angles obtuse; hind angles obtuse, well marked and protruding; basal border emarginated; lateral furrows larger than in T. terrabravensis ; basal fovea well marked. Chaetotaxy: the anterior seta is located in the second quarter and the posterior seta located in the hind angle. Elytra ovate with rounded shoulders, 1.64x wider than pronotum (females: 1.50x–1.70x) and 1.42x as long as broad (females: 1.29x–1.50x); apex rounded, lateral furrows canaliculated; striae all well marked and interstriae convex. Recurrent striae less curved than in T. terrabravensis , but well connected to the 5th. Chaetotaxy: umbilical series typical of Trechus ; preapical seta nearer the suture than to the apex; the first discal seta in the 3rd stria is located in the anterior quarter and the second discal seta approximately in the center. Aedeagus with apex of median lobe bent down (lateral view) ( Fig. 2 a); Left and right parameres with 4 setae each ( Fig. 2 b).

Ecological notes. The specimens were all sampled inside Algar do Morro Pelado, a volcanic pit of great dimensions (140 m deep) located at 1000 m a.s.l. ( Fig. 3 ). The surrounding area consists of natural grassland and is under the European NATURA 2000 network protection. The cave was visited in May and July 2004 during two biospeleological expeditions organized by GESPEA and “Os Montanheiros”. The pit has two large superimposed chambers. The lower and larger chamber has the darkest conditions (with 150 m x 70 m and about 50 m height) and is 140 m deep. The upper chamber is 30–40 m deep and has permanent access to sunlight with some darker parts. Due to logistics, only the upper chamber was sampled using 20 traps baited with fresh cow liver. All specimens were sampled alive in traps located deep inside the chamber, in very humid spots and protected from direct sunlight. The habitat is similar to that of Trechus jorgensis in the volcanic pit Algar das Bocas do Fogo (also in São Jorge, but at 385 m a.s.l.) and Trechus terceiranus in Algar do Carvão (Terceira).

Taxonomic notes. The new species, as well as T. montanheirorum , presents the median lobe of aedeagus (lateral view) with a similar form (cf. Fig. 2 a with Fig. 6 in Oromi & Borges 1991). However, particular features of the head and pronotum length and width, form and length of eyes and the location of the preapical setae of elytron, easily separate the two species ( Table 1 ). Besides length of body and some features of the eyes, pronotum and apical angle of elytron, the form of median lobe in lateral view (mainly the apex bent down) separates also the new species from all the others occurring in Azores. The general morphological aspect of T. isabelae n. sp. resembles also the epigean Trechus terrabravensis (endemic to Terceira island), but is larger and easily distinguishable by the larger size of the 3rd antennomere, which is longer than the 2nd. Taking into account the comparison of aedeagus and all analysed characters, the new species seems to have a closer relationship with T. montanheirorum (see also Amorim 2005), a species that occurs in a different but adjacent island (Pico).

Figures

FIGURE 1. Aspect of the male of Trechus isabelae n. sp. (Photo M. Ibáñez & H. López).

FIGURE 2. Aedeagus of Trechus isabelae n. sp. a) median lobe, lateral view; b) left and right parameres c) median lobe, dorsal view. Scale: 0.5 mm.

FIGURE 3. Location in the island of São Jorge (digital map of João Tavares adapted from Pereira et al. in press) and general aspect of Trechus isabelae n. sp. (Photo P. A. V. Borges).

FIGURE 6. Relationship between the logarithm of the mean abundance + 1 and the logarithm of distribution for the 10 Azorean species of Trechinae. The species within the quadrate are the most restricted and less abundant. The species marked with an open square is Trechus terrabravensis (see text for more details); 1 — Thalassophilus azoricus, 2 — Trechus torretassoi, 3 — Trechus jorgensis, 4 — Trechus pereirai, 5 — Trechus isabelae, 6 — Trechus montanheirorum, 7 — Trechus oromii, 8 — Trechus terrabravensis, 9 — Trechus picoensis, 10 — Trechus terceiranus.