Evolutionary dynamics of the karyotype of the wasp Trypoxylon (Trypargilum) nitidum (Hymenoptera, Sphecidae) from the Rio Doce State Park, Minas Gerais, Brazil

Abstract

Cytogenetic analysis based on the distribution of C-bands showed two groups of karyotypes in a Trypoxylon nitidum population from the Rio Doce Park, State of Minas Gerais, Brazil. One of these groups, that was identical to a previously described karyotype (n = 15; 2n = 30), had a stable chromosome number and was rich in acrocentric chromosomes, whereas the other had a variable chromosome number (n = 12 to 14; 2n = 25 to 28) and was rich in pseudo-acrocentric chromosomes. We propose a hypothesis explaining the dynamics of the modifications which occurred in the karyotype of this species, based on the minimum interaction theory of Imai et al. (1986Imai et al. ( , 1988Imai et al. ( , 1994 and on the chromosome rearrangements and heteromorphisms observed by us.

Occurrence of multiple nucleolus organizer regions and intraspecific karyotype variation in Scaptotrigona xanthotricha Moure (Hymenoptera, Meliponini)

“…However, most previous studies showed numeric variation as the main source of polymorphism (Brito et al, 1997;Araújo et al, 2002;Scher and Pompolo, 2003;Brown Jr. et al, 2004). The chromosome number 2n = 34 determined for Scaptotrigona xanthotricha agrees with previous studies on other Scaptotrigona species (Hoshiba and Imai, 1993;Rocha et al, 2003) and corroborates the numerical stability in the tribe Meliponini (Brito et al, 2003;Rocha et al, 2003;Costa et al, 2004).…”

“…In Hymenoptera, heterochromatin heteromorphism was observed in previous studies on the wasp Trypoxylon (Trypargilum) nitidum (Scher and Pompolo, 2003), and on the bees Partamona helleri (Brito et al, 1997) and Friesella schrottkyi (Mampumbu AR, unpublished results).…”

Molecular characterization of constitutive heterochromatin in three species of Trypoxylon (Hymenoptera, Crabronidae, Trypoxylini) by CMA3/DAPI staining

“…Specimens of Trypoxylon nitidum and Trypoxylon lactitarse showed a chromosome number within the range observed in this subgenus, whereas Trypoxylon rugifrons specimens showed the lowest chromosome number reported in the genus so far. The karyotypes and C-banding in Trypoxylon lactitarse and Trypoxylon nitidum from Camacanwere similar to those found by Gomes et al (1997) and Scher and Pompolo (2003) in the Brazilian Southeast region, revealing karyotype stability within these species along this range of the geographic distribution.…”

“…Araújo et al (2000) verified that the B chromosome in Trypoxylon albitarse was also stained by CMA3, similarly to the constitutive heterochromatin of all chromosomes in the complement, thus suggesting that the B chromosome originated from breaks in the constitutive heterochromatin and is maintained in the genome by centromeric “reactivation”. Scher and Pompolo (2003) did not report Trypoxylon nitidum specimens with 2n=29 in a population collected at the Parque Estadual do Rio Doce, in the state of Minas Gerais ( 19°30'S, 41°1'W ). This heterogeneity in karyotype over the distribution range highlights the need for further investigations in different localities to better resolve both karyotype distribution mapping and variation among Trypoxylon nitidum populations.…”

“…In Trypoxylon albitarse Fabricius, 1804, karyotype variation was due to the presence of B chromosomes ( Araújo et al 2000 ). Scher and Pompolo (2003) also found remarkable karyotype differences (n=12 to 15 and 2n =25 to 28 and 2n=30) in a population of Trypoxylon nitidum F. Smith, 1856 in southeastern Brazil. Heterochromatin has been shown to be highly variable in the hymenopterans and has been specially meaningful in the evolutionof Trypoxylon karyotypes due to its high content in some species ( Gomes et al 1995 , 1997, Scher and Pompolo 2003 ).…”