Formigas, fogo e seus efeitos sobre os invasores de termiteiros

The invasion of social insect nests by opportunistic species is a frequently reported phenomenon. This behavior allows the attacker to enjoy the benefits provided by the nest without dealing with the burden of its construction. Among the organisms associated with termite mounds are ants, arachnids, insects, crustaceans, and millipedes. The eusocial behavior of ants allows the recruitment of various colony individuals to defend territories and resources. When associated to termite mounds, ants can act as an indirect protection of mounds, reducing the success of invasions. Another factor that can affect the rate of térmite mounds invasions is fire. Fire affects fauna mainly by eliminating individuals, and may or may not affect species richness. Indirectly, it also affects the availability of resources by reducing the density of the vegetation cover, which could lead to increased rates of invasions by organisms looking for food resources and shelter. The aim of this study was to test the hypotheses that: I - the presence of contiguous ant nests reduces the termites mounds invasion rate by other organisms and II térmites mounds exposed to fire have higher invasion rate. It was collected 30 termite mounds , 15 present on burned areas and 15 at unburned areas at PARNA Serra do Cipo in Minas Gerais. Among the sampled nests , 19 had associated anthills, 9 from burned areas and 10 from unburned areas. The termite mounds were removed and placed in plastic bags for transportation. In laboratory they were kept frozen until sorting of the content. The organisms founded were identified and quantified. To establish the effects of fire and the presence of anthills on termite nests, GLM 's were built where the occurrence of fire and the presence of anthills were the explanatory variables and the richness of invaders and inquilines the response variables. There was no significant response of fauna to the occurrence of fires (P> 0.05), indicating that termite mounds are safe places for fauna during fires. However , the presence of anthills reduced the invaders richness (P < 0.05), but did not affect the inquilines richness The invasion of social insect nests by opportunistic species is a frequently reported phenomenon. This behavior allows the attacker to enjoy the benefits provided by the nest without dealing with the burden of its construction. Among the organisms associated with termite mounds are ants, arachnids, insects, crustaceans, and millipedes. The eusocial behavior of ants allows the recruitment of various colony individuals to defend territories and resources. When associated to termite mounds, ants can act as an indirect protection of mounds, reducing the success of invasions. Another factor that can affect the rate of térmite mounds invasions is fire. Fire affects fauna mainly by eliminating individuals, and may or may not affect species richness. Indirectly, it also affects the availability of resources by reducing the density of the vegetation cover, which could lead to increased rates of invasions by organisms looking for food resources and shelter. The aim of this study was to test the hypotheses that: I - the presence of contiguous ant nests reduces the termites mounds invasion rate by other organisms and II térmites mounds exposed to fire have higher invasion rate. It was collected 30 termite mounds , 15 present on burned areas and 15 at unburned areas at PARNA Serra do Cipo in Minas Gerais. Among the sampled nests , 19 had associated anthills, 9 from burned areas and 10 from unburned areas. The termite mounds were removed and placed in plastic bags for transportation. In laboratory they were kept frozen until sorting of the content. The organisms founded were identified and quantified. To establish the effects of fire and the presence of anthills on termite nests, GLM 's were built where the occurrence of fire and the presence of anthills were the explanatory variables and the richness of invaders and inquilines the response variables. There was no significant response of fauna to the occurrence of fires (P> 0.05), indicating that termite mounds are safe places for fauna during fires. However , the presence of anthills reduced the invaders richness (P < 0.05), but did not affect the inquilines richness (P> 0.05) indicating that defensive postures of ants though inhibit the installation of invaders, are not directed against termites.(P> 0.05) indicating that defensive postures of ants though inhibit the installation of invaders, are not directed against termites.

A invasão de ninhos de insetos sociais por espécies oportunistas é um fenômeno reportado com bastante freqüência. Tal comportamento permite que o invasor usufrua dos benefícios providos pelo ninho sem lidar com o fardo de sua construção. Dentre os organismos associados aos termiteiros estão as formigas, aracnídeos, diversos insetos, crustáceos, miriápodes dentre outros. O comportamento eusocial das formigas permite o recrutamento de vários indivíduos da colônia para a defesa de territórios e recursos. Ao se associarem a termiteiros podem atuar como defesa indireta dos mesmos reduzindo o sucesso das invasões. Outro fator que pode afetar a taxa de invasões de termiteiros é o fogo. O fogo atua sobre a fauna principalmente através da eliminação de indivíduos, podendo ou não afetar a riqueza de espécies. De forma indireta, afeta a disponibilidade de recursos através da redução do adensamento da cobertura vegetal, fato que poderia levar a uma elevação da taxa de invasões por organismos à procura de recursos alimentares e abrigo. O objetivo deste estudo foi testar as hipóteses de que: I - a presença de formigueiros contíguos aos termiteiros reduziria a taxa de invasão de termiteiros por outros organismos e II - termiteiros expostos a queimadas apresentariam maior taxa de invasão. Foram coletados 30 termiteiros, 15 presentes em áreas queimadas e 15 em áreas não queimadas no PARNA Serra do Cipó em Minas Gerais. Dentre os ninhos amostrados, 19 apresentavam associação com formigueiros, sendo 9 em áreas queimadas e 10 em áreas não queimadas. Os termiteiros foram removidos e acondicionados em sacos plásticos para o transporte. Em laboratório foram mantidos congelados até a triagem do conteúdo. Os organismos presentes foram identificados e quantificados. Para se estabelecer os efeitos do fogo e da presença de formigueiros nos termiteiros, foram construídos GLMs sendo a ocorrência de queimadas e a presença de formigueiros as variáveis explicativas e a riqueza de invasores e inquilinos as variáveis resposta. Não houve resposta significativa da fauna à ocorrência de queimadas (P>0,05. No entanto, a presença de formigueiros reduziu a riqueza de invasores (P<0,05), porém não afetou a riqueza de inquilinos (P>0,05). Assim, embora afete severamente o ambiente, o fogo tem seus efeitos amortecidos pela estrutura dos termiteiros. As posturas defensivas das formigas embora inibam a instalação de invasores, não são direcionadas aos cupins.