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| Crossodactylodes alairi Santos, Gehara, Oswald, Ferreira, Santos, Garcia, Zamudio, Haddad & Magalhães, 2025 |
ABSTRACT
The Atlantic Forest domain is a biodiversity hotspot with remarkable amphibian diversity, including over 700 species, 70% of which are endemic. Most of these endemic species have restricted geographic ranges, often confined to mountainous areas, as exemplified by the leptodactylid genus Crossodactylodes. These frogs are characterised by small body sizes, a bromeligenous habit and limited dispersal abilities, with species often restricted to their type localities. Previous studies have revealed geographically structured lineages within the genus, even when separated by short distances. Here, we focused on a clade of Crossodactylodes comprising three lineages from southeastern Brazil, inhabiting montane forest ‘islands’ distinct from surrounding lowland areas regarding vegetation structure and microclimate. We integrated genetic, geographic, morphometric and qualitative morphological data to assess species boundaries through species delimitation analyses and validation procedures. This integrative approach provided evidence supporting the recognition of one lineage as a distinct taxonomic entity, which we formally describe herein as Crossodactylodes alairi sp. nov. Additionally, we applied coalescent simulations and supervised machine-learning approaches to evaluate alternative diversification hypotheses. Our results provide strong support for fragmentation models, suggesting that divergences within the focal lineages were driven by climate-related habitat fragmentation during the Plio-Pleistocene. Given that these lineages inhabit a non-macrorefugium region of the Atlantic Forest, their evolutionary trajectories were likely shaped by survival in isolated microrefugia that offered stable and suitable microclimatic conditions amidst broader environmental changes.
Keywords: Anura, integrative taxonomy, microendemism, microrefugia, Paratelmatobiinae, speciation, species delimitation
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| Geographic distribution of the three lineages addressed in this study (FG, ST and SL), which occur on distinct mountaintops within the Atlantic Forest in the state of Espírito Santo, southeastern Brazil. The inset in the bottom right corner shows the vegetation structure in the locality where lineage SL occurs, characterised by low trees, the presence of shrubs and lichens and a high density of epiphytic and ground bromeliads (photo: A. P. Araújo). |
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| Crossodactylodes alairi sp. nov., holotype in life (UFMG-AMP 14201, male, SVL 21.1 mm). |
Crossodactylodes alairi sp. nov.
Crossodactylodes bokermanni—Almeida et al. (2011, 557 [their appendix 1], in part);
Montesinos et al. (2012, 112 [their appendix 1]).
Diagnosis. Crossodactylodes alairi is diagnosable from its congeners by the following combination of characters: (1) absence of vomerine odontophores; (2) adult males lacking vocal slits; (3) absence of dorsolateral fold; (4) inner metacarpal tubercle in adult males weakly widened; (5) discs of fingers II–IV slightly expanded; (6) hindlimbs lacking transverse bars; (7) skin on males dorsum coarsely granular; (8) SVL 17.2–18.6 mm (females) and 17.0–21.1 mm (males); (9) in life, iris uniformly dark brown or light brown with dark brown fine reticulations; (10) upper eyelid margin granular, with a pronounced tubercle in its medial region; (11) disc of Finger I rounded; (12) medial region of the upper lip not anteriorly projected.
Etymology. The specific epithet honours Alair Tedesco, a park ranger who worked at Parque Estadual do Forno Grande for 27 years, dedicating much of his life to conserving the region. Even in retirement, he continues to collaborate with researchers and visitors, enthusiastically sharing his vast knowledge of the area.
Suggested common names: Alair's bromeliad frog (English); rãzinha-de-bromélia-de-Alair (Portuguese).
Marcus Thadeu T. Santos, Marcelo Gehara, Caroline B. Oswald, Rodrigo B. Ferreira, Fabrício R. Santos, Paulo C. A. Garcia, Kelly R. Zamudio, Célio F. B. Haddad and Rafael F. Magalhães. 2025. Historical Fragmentation in Atlantic Forest Explains the Diversification of a Clade of Mountaintop Bromeligenous Frogs (Leptodactylidae: Crossodactylodes). Zoologica Scripta. DOI: doi.org/10.1111/zsc.70001 [11 July 2025]
