Tyrannoseira, Bellini & Zeppelini, 2011

Bellini, Bruno Cavalcante & Zeppelini, Douglas, 2011, New genus and species of Seirini (Collembola, Entomobryidae) from Caatinga Biome, Northeastern Brazil, Zoosystema 33 (4), pp. 545-555 : 547-552

Genus Tyrannoseira n. gen.

DIAGNOSIS. — Entomobryid habitus, with body covered by yellowish to brownish apically rounded scales. Eyes 8 + 8. Head chaetotaxy with M2 micro- or mesochaetae, S0-S3 always as macrochaetae, resulting in a cephalic region 4 with a total of 7 macrochaetae ( Figs 1; 6 ). Femora of the first pair of legs on males variably enlarged, bearing a variable number of short and strong spines, concentrated on a ventral projection of the femora ( Figs 2; 4F ). First pair of tibiotarsi curved on males, bearing a single row of long spine-like setae ( Figs 2; 4G ). Ungues with four inner teeth, two of them unpaired and two paired at the med-line of the structure. Unguiculi acuminate with weakly serrated edges.Tenent-hairs strong and capitate with slightly serrated edges. Absence of macrochaetae on the first abdominal segment of adults ( Figs 1; 6 ). Dens crenulate, mucro falcate, without dental or mucronal spines ( Fig. 4J ).

TYPE SPECIES. — Seira raptora Zeppelini & Bellini, 2006 .

OTHER SPECIES OF THE GENUS. — Tyrannoseira bicolorcornuta (Bellini, Pais & Zeppelini, 2009) n. comb., described as Seira bicolorcornuta ; T. sex n. sp.

ETYMOLOGY. — From the Greek tyrannos: ruler, usurper. Seira refers to the clear relationship with the type genus of Seirini.

DISTRIBUTION. — Caatinga biome, Northeastern Brazil. Good’s biogeographic zone 27 ( Good 1974).

HABITAT. — The three known species of Tyrannoseira n. gen. are restricted to Caatinga biome, a semi-arid region exclusively seen in Brazil inside or nearby a sub-region named “Planalto da Borborema”. This area is known by a rocky irregular and preeminent relief. The climate of the area is “As” following Koeppen’s system, which means an equatorial predominant climate and the precipitation with a clear “dry summer” annual season (Kottek et al. 2006).

REMARKS

Tyrannoseira raptora n. comb. was originally in Seira and it fits the current diagnoses of the genus ( Zeppelini & Bellini 2006). On the other hand the species, T. bicolorcornuta n. comb. and T. sex n. sp. are clearly part a of monophyletic lineage inside the genus, as they show a unique type of sexual dimorphism among the Entomobryidae . Other species of Seira , like S. domestica Nicolet, 1842 , S. mantis Zeppelini & Bellini, 2006 and S. uwei Barra, 2010 also show sexual dimorphic legs ( Gisin & Gama 1962; Zeppelini & Bellini 2006; Palacios-Vargas & Castaño Meneses 2009; Barra 2010), but the morphological condition seen in Tyrannoseira n. gen. is strikingly different from that of S. domestica and related species, suggesting a convergent origin of similar sexual dimorphism in both taxa. The most remarkable difference is seen in male femora, being enlarged with short strong spines emerging from a single spot on the ventral side of each femur in Tyrannoseira n. gen. as opposed to normal-shaped femora with large spines in a single row in S. domestica group (see Zeppelini & Bellini 2006 and Barra 2010). The tibiotarsi also show important differences. In Tyrannoseira n. gen., the tibiotarsi are clearly curved at the apex and there is only a single row of long spines ( Zeppelini & Bellini 2006; Bellini et al. 2009). In the domestica group, there are several short spines inside three rows at the apex of the tibiotarsi, and the size of spines in the structure is significantly smaller than in Tyrannoseira n. gen. ( Gisin & Gama 1962; Zeppelini & Bellini 2006; Barra 2010). Despite the size and number of spines, these differences on the legs of both groups also point to a more important feature: many spines, which are originated from setae, are clearly not homologous in Tyrannoseira n. gen. and the domestica group. To support this theory, there are several important differences on the dorsal chaetotaxy of both groups. There are obvious differences in the distribution of dorsal macrochaetae in all segments, but there is a pattern within each group, especially on the head (7 macrochaetae in Tyrannoseira n. gen. and 9 macrochaetae in the domestica group on cephalic region 4) and abdominal segment I (no macrochaetae in Tyrannoseira n. gen. and 6 + 6 macrochaetae in the domestica group). In fact, the constant morphology showed by the domestica group indicates that it is very likely that this set of species also forms a monophyletic lineage inside Seira .

Our preliminary studies showed that males of T. raptora n. comb. use the first pair of legs, modified into a clasping organ, to grab other males during intrasexual agonistic behavior, when they fight for feeding areas ( Fig. 3 ). This behavior possibly increases access to females, while at the same time it limits the number of reproductive competitors. We expect the same behavior in other members of the new genus.

Our laboratory and field observations showed many important features on the behavior of T. raptora n. comb. and Seira species that can explain the selection of modified legs in males and the dual origin of this feature in the whole group. First, species of both genera and possibly most Seirini are very active during day time. Aggressive intraspecific behavior was observed in T. raptora n. comb., S. mirianae Arlé & Guimarães, 1981, S. mendoncea Bellini & Zeppelini, 2009 , S. nigrans Arlé, 1960 and S. potiguara Bellini et al., 2010 (Bellini & Zeppelini, unpubl.). The females of T. raptora n. comb., which lacks the modified legs, can also fight grabbing each other when they protect feeding areas. We didn’t observe the behavior of males grabbing each other in species other than T. raptora n. comb., but the behavior of the females of this last species suggests it is very likely that it occurs in some Seira species. In these particular cases, any morphological modification which raises the efficiency in the fights, like the emergence of spines or modifications in the form of the structure to increase the efficiency of grabbing, would be rapidly incorporated into the populations as the males bearing them have higher rates of success during the reproduction process. That would explain the convergent origins of the modified legs in Tyrannoseira n. gen. and in the domestica group and makes possible the discovery of other groups among the Seirini with minor or major modifications to increase the fitness of the structure.

The combination of head chaetotaxy with mesochaetae M2 as and macrochaetae S0 to S3, and the lack of macrochaetae on abdominal segment I is not exclusive to Tyrannoseira n. gen. Two other neotropical Seira species, S. mirianae and S. andensis Jacquemart, 1980 also have the same combination of characters ( Christiansen & Bellinger 2000) shown in Table 1. The overall dorsal chaetotaxy of both species is similar to that in Tyrannoseira n. gen. spe- cies. It is very likely that S. mirianae, a sympatric species to T. raptora n. comb., is closely related to Tyrannoseira n. gen. However, only a phylogenetic analysis of Seira and Tyrannoseira n. gen. could provide support to this hypothesis.

Seira comprises more than 180 described species, many of which are incompletely described. This makes it difficult to produce a rapid and clear comparison among the species. Therefore, a phylogenetic revision and subdivision of the genus into manageable taxonomic groups is urgent. Seira is divided into three subgenera (Afroseira Yosii, 1959, Lepidocyrtinus Börner, 1903 and Seira s.s.) ( Yosii 1959), but they are not well accepted and rarely used in current taxonomic work ( Christiansen & Bellinger 2000; Barra 2004 a, b; Negri et al. 2005; Zeppelini & Bellini 2006; Bellini & Zeppelini 2008 a, b, 2009 b; Soto-Adames et al. 2008; Bellini et al. 2009, 2010). The most remarkable problem with this subdivision is the large number of species retained in Seira s.s. Afroseira is represented by only one species, S. rowani Yosii, 1959, which lacks the distal pair of botriothrica on the fourth abdominal segment. This particular morphology is probably a pedomorphic character on Seirini, since the first instar of some species (probably all) like S. dowlingi Wray, 1959 ( Soto-Adames 2008) and T. raptora n. comb. lacks these botriothrica. Lepidocyrtinus is a group of frequently elongated body species of Seira with large blunt setae on the dens, and less than 10 fitting species ( Arlé 1959; Yosii 1959; Bellinger et al. 1996 - 2010; Christiansen & Bellinger 2000). In South America, three species of Lepidocyrtinus were described by Arlé (1959) as Ctenocyrtinus, a genus posteriorly synonymized with Seira by Christiansen & Bellinger (2000). While Afroseira and probably Lepidocyrtinus are monophyletic groups, they are not helpful in making easier the identification of many Seira species. The small monophyletic groups represented by Afroseira, Lepidocyrtinus and Tyrannoseira n. gen., leaves a paraphyletic Seira s.s. and a phylogenetic analysis of the whole group is needed to shade some light in the relationship in Seirini and test the monophyly of Seira s.s.

Figures

FIG. 1. — Dorsal macrochaetae distribution of: A, Tyrannoseira raptora (Zeppelini & Bellini, 2006) n. comb.; B, T. bicolorcornuta (Bellini, Pais & Zeppelini, 2009) n. comb.

FIG. 6. — Dorsal macrochaetae distribution of Tyrannoseira sex n. sp.

FIG. 2. — Femur and tibiotarsus of the first pair of legs of males of: A, Tyrannoseira raptora (Zeppelini & Bellini, 2006) n. comb.; B, T. bicolorcornuta (Bellini, Pais & Zeppelini, 2009) n. comb. Scale bars: A, B, 10 μm.

FIG. 4. — Tyrannoseira sex n. sp.: A, habitus; B, apical bulb of the 4th antennal segment; C, right eye patch; D, labial papillae;E, setae of the labial triangle; F, anterior femur of males; G, anterior tibiotarsus of the males; H, trochanteral organ; I, second foot complex; J, distal dens with mucro. Scale bars: A, 100 μm; B-J, 10 μm.

FIG. 3. — Males of Tyrannoseira raptora (Zeppelini & Bellini, 2006) n. comb. fighting: A, males grabbing each other to strike with legs, antennae and furca; B, male grabbing an antenna of another male. Scale bars: A, B, 100 μm.