Juliana Maria Conceição Alves

The lesion nematode Pratylenchus brachyurus exhibits significant intraspecific variability in both morphology and genetic constitution and causes substantial damage to several crops in Brazil, including coffee and cotton. This study investigated the intraspecific variability of P. brachyurus populations with distinct geographic origins, originally collected from coffee and cotton fields, through morphometric and molecular characterizations, in order to evaluate the genetic variability of these populations. Four populations of P. brachyurus were evaluated: three originally sampled from coffee fields in São Paulo state (Dracena – PbDR, Franca – PbFR, and Garça – PbGA) and one originally collected from cotton field in Bahia (São Desidério – PbSD). Intraspecific variability was characterized by morphometric studies as well as molecular analyses of the ITS-1 region. The morphometric analyses revealed greater similarity among populations PbDR, PbFR, and PbSD in relation to PbGA, whereas the molecular analyses highlighted genetic variation among populations and intra-individual variability among ITS-1 clones obtained from the single PbGA female analyzed. The existence of intraspecific variation among P. brachyurus populations was demonstrated using an integrative taxonomy approach, combining morphometric and genetic evidence.

Ants of the genus Solenopsis are globally distributed, presenting high diversity and many generalist species. In South America, the dominant species is Solenopsis saevissima (Smith, 1855), commonly found nesting in grassy fields surrounding humanized areas. In spite of being so common, there has been no research evaluating the effect of human disturbances on the mitochondrial DNA (mtDNA) haplotype diversity in this species. In this context, we here characterized the mtDNA haplotype diversity in S. saevissima nests by highway roadsides, dust roads, and forest borders of Atlantic Forest, based on partial sequences of cytochrome c oxidase subunit I (COI). Based on the facts that the species is a rapid colonizer of disturbed habitats, we specifically probed how the genetic diversity of native S. saevissima is impacted by highways and roads infrastructure expanding around the rainforest. Species diagnosis was established both by morphological characters and obtained mtDNA COI sequences. Overall, the species exhibited high haplotypes and nucleotide diversity, particularly around forest borders; though all haplotypes seemed closely related across the different habitats. We identified seven mitochondrial haplotypes (H1 to H7), where haplotype H1 was exclusively found in highway roadside nests, and H7 on dust roads; the remaining haplotypes were recorded from all habitats. Haplotype H1 was geographically isolated to the south of the Atlantic Forest, supporting previous suggestions that it acts as a biogeographical barrier. The pattern is suggestive of a recent species expansion, probably resulting from extensive habitat fragmentation. Taken together, our data demonstrates fire ant haplotypes prevailing in some anthropized habitats, characterizing how a native species lining the remnants of the Brazilian Atlantic Forest might be a concern for environmental conservation.

The present investigation deals with some aspects of the diversity of fire ants (Hymenoptera: Formicidae) in their native range. The Red Imported Fire Ant Solenopsis invicta is native to the tropical and subtropical inland territories of South America. In Brazil, it mainly occurs around the Pantanal region and across the Paraguay river, a region composed of grasslands which are seasonally flooded. Recent studies have evidenced this fire ant species is gradually spreading to other regions of Brazil. In the present investigation, we surveyed the molecular diversity of S. invicta populations across fragments of Atlantic Forest in São Paulo, Brazil, using mtDNA COI haplotypes. Fire ant nests were sampled along the highways lining the northern and southern slope sides of the mountain range Serra do Mar, SP, Brazil. Four haplotypes were identified (H1–H4), which were assessed for similarity to deposited records by other authors, revealing that the haplotypes H1 and H2 are likely of foreign origin through recent reintroduction via a marine port to the south of the Serra do Mar mountain range. On the other hand, the haplotypes H3 and H4, predominating among the inland samples from the northern side of the mountain range, were most similar to previous records from more central regions of Brazil. Haplotypes clustered into distinct supergroups, further pointing to the occurrence of two separate expansion waves of S. invicta in the region. We suggest the obtained pattern indicates the mountain range may function as a geographical barrier deferring gene flow.

Solenopsis invicta and Solenopsis saevissima are the most common fire ants in Brazil. Environmental disturbances favour the colony dispersal of both species, particularly those with an anthropogenic origin. However, the frequencies of the species can vary according to the amount of anthropogenic disturbances. Crops near native vegetation fragments is a common landscape in the Brazilian Atlantic Forest. Here, we analyse if there is influence of native vegetation cover on the occurrence of these fire ants and their molecular diversity in crops. Our hypothesis is that these species are antagonistic in terms of occurrence and molecular diversity when compared in the same habitat. We selected crops near fragments with around 50% of native vegetation cover, a percentage informative enough to detect biological responses from insects belonging to a same order. Nests were collected and the species were identified using external morphology, and mtDNA COI sequences. We reject our hypothesis, which suggest that the species colonize the vegetation patches around crops in a similar way. Solenopsis invicta is not limited by vegetation cover, and has a high haplotype diversity when compared to S. saevissima , particularly when the vegetation cover is greater than 50%. Additionally, the vegetation cover seems to not have influence in the total number of haplotypes, but the species have haplotypes that are exclusive to each landscape. Our findings suggest that S. invicta is expanding to native vegetation areas that it has not occupied before, as S. saevissima was dominant there.

In South America, Solenopsis saevissima and S. invicta are the most common fire ants. Nests are founded in areas under anthropic interference like urban or rural areas, but S. invicta is found preferentially in those with the greatest anthropic interference. However, we do not know the rates at which they exist in anthropized areas next to high density of native vegetation. Areas with 60 to 90% of native Atlantic Forest were selected to verify the occurrence of both species in rural and urban areas. We investigated the molecular diversity and applied the reconstruction of the ancestral state analysis for each species. A total of 186 nests were analyzed and we found that the two species had the same proportion in the urban area. However, S. saevissima had a higher rate of prevalence in the rural area, in addition to having a greater number of haplotypes and ancestry associated with this type of habitat for the region. S. invicta had the same number of haplotypes in both rural and urban regions, and less haplotypic diversity. We conclude that S. saevissima is a species typically associated with rural areas and S. invicta, although present, is not dominant in urban areas.