Results
After filtering, the final ASV table encompassed 3923 unique ASVs,
included in a total of 39 bacteria phyla. The most abundant phyla were
Firmicutes, Bacteroidota, Actinobacteroidota, Proteobacteroidota and
Campylobacterota (Fig. 2)
Gut bacterial alpha-diversity was significantly different between Moledo
populations (P. bocagei and P. lusitanicus ) and Lisbon
populations (P. siculus , P. virescens and T.
dugesii ) (Table 1). Lisbon populations, those from an urbanized
habitat, showed consistently higher alpha-diversity indices, withP. siculus having higher diversity than the native P.
virescens. (Fig. 3). Microbial beta-diversity was also significantly
different between localities when considering the Bray-Curtis
(R2 = 0.186, p < 0.001) and the Unifrac
unweighted (R2 = 0.180, p < 0.001) indices
(Fig. 4 and Table 1).
Although no differences were found in the proportion of the most
abundant phyla between P. bocagei and P. lusitanicus ,
significant differences were found in the proportion of the genusCorynebacterium (F-statistics = 6.823, p = 0.013) (Fig. 5).
Differences in the proportion of the most abundant taxa between P.
siculus and P. virescens were found at genus levels for an
unidentified genus belonging to the order Gastranaerophilales
(F-statistics = 6.324, p = 0.003), Corynebacterium (F-statistics
= 6.887, p = 0.002), Kocuria (F-statistics = 4.639, p = 0.0138),Staphylococcus (F-statistics = 6.767, p = 0.002), andOdoribacter (F-statistics = 11.609, p = 6.398e-05) (Fig. 6).
Additionally, for P. siculus and P. virescens, both
species and sex significantly affected the abundance ofAkkermansia (sex: F-statistics = 5.191, p = 0.026; species:
F-statistics = 3.467, p = 0.038) (Fig 6 and 7) and the interaction
between species and sex (species*sex) significantly affected the
proportion of Romboutsia (F-statistics = 3.475, p = 0.038) andPseudomonas (F-statistics = 3.412, p = 0.040) (Fig. 7).
Pearson correlation test only showed significantly positive correlations
between SVL and bacterial alpha-diversity (for Shannon indice) for males
of the in the invasive species P. siculus (Fig. 8).
Results from FEAST software indicate that the level of bacterial
transmission between sympatric species in both populations (Parque das
Nações and Moledo) was high. Nevertheless, while between the syntopicP. lusitanicus and P. bocagei bacterial transmission was
balanced in both directions (P. bocagei P. lusitanicus~ 71% on average, and P. lusitanicus P.
bocagei ~ 69% on average), the other two sympatric
species showed a more biased transmission, with P. virescenshaving a higher contribution towards P. siculus (P.
virescens P. siculus of 72% on average, and P. siculusP. virescens of about 55% on average).