INVESTIGADORES
POMPOZZI Gabriel Alejandro
congresos y reuniones científicas
Título:
ETHOLOGICAL REPRODUCTIVE ISOLATION BETWEEN TWO POSSIBLE SYMPATRIC SPECIES OF GRAMMOSTOLA (ARANEAE: THERAPHOSIDAE) IN BUENOS AIRES, ARGENTINA
Autor/es:
NELSON FERRETTI; SOFÍA COPPERI; GABRIEL POMPOZZI; FERNANDO PÉREZ-MILES
Lugar:
Alexandroupoli
Reunión:
Congreso; 25th European Congress of Arachnology; 2009
Institución organizadora:
Democritus University of Thrace
Resumen:
<!--
/* Font Definitions */
@font-face
{font-family:"Cambria Math";
panose-1:2 4 5 3 5 4 6 3 2 4;
mso-font-charset:1;
mso-generic-font-family:roman;
mso-font-format:other;
mso-font-pitch:variable;
mso-font-signature:0 0 0 0 0 0;}
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;
mso-font-charset:0;
mso-generic-font-family:swiss;
mso-font-pitch:variable;
mso-font-signature:-520092929 1073786111 9 0 415 0;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{mso-style-unhide:no;
mso-style-qformat:yes;
mso-style-parent:"";
margin-top:0cm;
margin-right:0cm;
margin-bottom:10.0pt;
margin-left:0cm;
line-height:115%;
mso-pagination:widow-orphan;
font-size:11.0pt;
font-family:"Calibri","sans-serif";
mso-ascii-font-family:Calibri;
mso-ascii-theme-font:minor-latin;
mso-fareast-font-family:Calibri;
mso-fareast-theme-font:minor-latin;
mso-hansi-font-family:Calibri;
mso-hansi-theme-font:minor-latin;
mso-bidi-font-family:"Times New Roman";
mso-bidi-theme-font:minor-bidi;
mso-fareast-language:EN-US;}
.MsoChpDefault
{mso-style-type:export-only;
mso-default-props:yes;
mso-ascii-font-family:Calibri;
mso-ascii-theme-font:minor-latin;
mso-fareast-font-family:Calibri;
mso-fareast-theme-font:minor-latin;
mso-hansi-font-family:Calibri;
mso-hansi-theme-font:minor-latin;
mso-bidi-font-family:"Times New Roman";
mso-bidi-theme-font:minor-bidi;
mso-fareast-language:EN-US;}
.MsoPapDefault
{mso-style-type:export-only;
margin-bottom:10.0pt;
line-height:115%;}
@page WordSection1
{size:612.0pt 792.0pt;
margin:70.85pt 3.0cm 70.85pt 3.0cm;
mso-header-margin:36.0pt;
mso-footer-margin:36.0pt;
mso-paper-source:0;}
div.WordSection1
{page:WordSection1;}
-->
At the
south of the Buenos Aires
province are present two species of tarantulas, Grammostola doeringi
Holmberg 1881 and Grammostola schulzei (Schmidt, 1994). Grammostola
schulzei is a spider that inhabit burrows made always under stones in rocky
hills, in Sierra de la Ventana (38º 07 63 S 61º 47 30 W), Ventania, while Grammostola
doeringi is present at the outskirts of Bahía Blanca (38° 44 30 S 62° 12
31 W), where it lives in burrows made in open field at the pampas. Recently,
some individuals of Grammostola schulzei were found living near Bahia
Blanca and individuals of Grammostola doeringi in Sierra de la Ventana.
These findings suggested us that must exist an overlapping zone in which the
species are sympatric. In addition, the sexual period of these species overlaps
in time; walking males can be found during October December (late spring and
early summer in South Hemisphere). Reproductive isolation mechanisms are
especially important in sympatric and synchronic species since they provide
insights into the process speciation in singular conditions. Moreover,
differences in reproductive isolating traits are expected to be greater in
sympatry than in allopatry. This pattern of sympatric divergence arises from selection
against the adverse consequences of hybridization between sympatric species. In
Theraphosidae, the reproductive isolation was examined under laboratory
conditions for three populations of Grammostola mollicoma and Grammostola
iheringi occurring in Uruguay, where no isolation was found on G.
mollicoma due to their poor knowledge on
distribution of these populations, but G. iheringi showed an effective
ethological reproductive isolation. The main objective of this work is to test
if the species mentioned have ethological mechanisms of isolation under
laboratory conditions. We studied males courtships and females responses in
conspecific and heterospecific encounters. We used five males and eight females
of G. doeringi and four males and ten females of G. schulzei.
Individuals were randomly assigned to pairs. So, males of the two species were
in contact with conspecific and heterospecific females in all possible
combinations. The interactions between individuals were carried out in cages of
30 x 35 and 30 cm high, with a layer of soil of 10 cm deep and a burrow was
excavated against the glass wall allowing for observation. Encounters were
videotape and analyzed. Males courted on silk tracks of conspecific and
heterospecific females. Both males of G. doeringi and G. schulzei
showed approximately same frequencies of bouts in all interactions during
courtship. However G. schulzei displayed palpal drumming and palpate,
while G. doeringi only palpated. Grammostola doeringi performed
more leg tapping and palpating with conspecific than with females of G.
schulzei. On the other hand, G. schulzei courted more vigorously to
females of the other species than conspecific. None of females called males,
and the acceptation of males for mating was given by the female leaving the
burrow, raising her body and opening fangs. Usually mating takes place outside
the burrow due to spatial constrains. When heterospecific males entered to the
burrow, females beat them with the first pair of legs and males escaped without
injuries. Moreover, sometimes females leaved their burrows when confronting a
heterospecific male; then females raised their bodies but didn´t open her
fangs, so that males failed to clasp and moved away. On those cases, females
didn´t reach the immobile condition and usually attacked males (3 females of G.
schulzei) and even predated them (2 females of G. schulzei). Females
of G. doeringi were more passive and didn´t showed aggression. We
registered one interspecific mating, with a male of G. doeringi and a
female of G. schulzei, with regular posture and insertions. Usually an
ethological isolation mechanism operated after physical contact, although it
could exceptionally fail. In this case, the cost in energy, time and risk is
high for the couple and especially for female. An alternative interpretation of
this failure could be a female strategy for predation on heterospecific males.