Models
The site with the highest value of BGF concordance was Galinhos (05°03’ S, 36°45’ W); north of Rio Grande do Norte State (27 %). The linear model identified a statistically significant negative relationship between frequency in the occurrence of phylogenetic breaks (BGF) and latitude, R2 = 0.4, p < 0.001 (Fig. 4).Gam results from all data combined (= total analysis) identified four geographic regions with distinct patterns of BGF frequency distribution along the Brazilian coast, herein dubbed phylogeographic Regions I-IV (Fig. 5). Anova detected significant differences in the average amount of BGF frequencies among these regions. Pairwise tests found no differences between Regions I and II but Regions III and IV where different from all the others (Fig. 6). Gam Region I (0° S – 10° S) was located in northern Brazil and presented a bell-shaped BGF frequency distribution with the greatest modelled values of BGF concordance in the entire Brazilian coast. Gam identified Natal city in central Rio Grande do Norte (05° 46’ S) as the region with the highest value of BGF concordance (Fig. 5). Region II showed a relative homogenous distribution of BGF concordances south of 10° S until the Vitória-Trindade seamount chain region at 20.5° S. Region III (20.5° S - 27° S) exhibited an inverted bell-shaped distribution with the lowest BGF concordance values, ranging from central Espírito Santo to northern Santa Catarina (Itajaí: 26° 54’ S). Region IV was characterized by a moderate bell-shaped distribution of BGF concordance values that started at northern Santa Catarina and extended to the north-end of longest uninterrupted sandy seashore in the world (Patos lagoon inlet: 31° 22’ S). In Region IV the gam maximum BGF concordance value occurs in southern Santa Catarina, Cape Santa Marta, 28° 36’ S (Fig. 5).
Gam for the four most studied taxa (fishes, crustaceans, mollusks, and cnidarians) produced patterns of BGF frequency distribution similar to those reported in the total analysis, although slightly differences were noted (Figs. 7A-D). Fishes, the most data-rich taxon (Fig. 7A), presented the I-IV region pattern reported in the total analysis but the main peak of maxima was observed at the southern-end of Region II, around central Rio de Janeiro (Saquarema: 22° 56 S, 42° 29 W), followed by a slightly lower maxima in Region I. Latitudes or a string of adjacent sites with values of BGF frequency distribution equal to 0% identifies regions of widespread panmixia, and that was the case for fish populations sampled between Paraná (Laranjeiras Bay: 25° 24’ S) and northern Santa Catarina (Itajaí: 26° 54’ S). A thirst albeit small maxima was also observed inside Region II, coinciding with central Bahia state (Barra Grande: 13° 52’ S). Accordingly, fishes’ gampresented four regions of BGF frequency maxima: northern Rio Grande do Norte (around Galinhos: 05° 03’ S, 36° 45’ W), central Bahia (around Barra Grande: 13° 52’ S), central Rio de Janeiro (around Saquarema: 22° 56 S, 42° 29 W), and southern Rio Grande do Sul (near Patos lagoon inlet: 31° 22’ S) (Fig. 7A).
Even though the crustacean gam presented similar topology to those obtained from the other three taxa and the total evidencegam , this taxon showed slightly unique pattern of BGF frequency distribution (Fig. 7B). The greatest modelled BGF frequency value for crustaceans along the Brazilian coast occurred near Cape Santa Marta, 28° 36’ S (23%), in phylogeographic Region IV. The north and northeastern Brazilian coast showed a somewhat homogenous BGF frequency distribution ranging from Pará (Belém: 01° 24’ S), to south Espírito Santo (Guarapari: 20° 40’ S) (Fig. 7B). An increase in the values of crustacean BGF frequency, denoting a bell-shape topology, was observed in southeastern Brazil, starting in Guarapari (Espírito Santo), peaking at central Rio de Janeiro (within the Cabo Frio district, 22° 57’ S) and ending in northern São Paulo (Ubatuba: 23° 26’ S) (Fig. 7B). A long region of lower BGF frequencies (similar total dataset Region III) occurred south of Ubatuba (São Paulo) and extended to north Santa Catarina (Itajaí: 26° 54’ S).
For mollusks and cnidarians, recorded BGF values in the literature are absent west of Belém (01° 27’ S, 48° 29’ W) and Fortaleza (03° 43’ S, 38° 31’ W), respectively, and south of Florianópolis (27° 36’ S) for both groups (Figs. 7C and 7D). Gam results for mollusks and cnidarians presented several similarities. Mollusks and cnidarians showed the greatest values of BGF frequency distribution in their northernmost latitudes within Brazil (phylogeography Region I in the total evidence gam ), with maximum values reaching 50% and 75%, respectively. For mollusks, the maximum BGF concordance occurred around west of Fortaleza at Ceará state, all the way to Maranhão state (Fig. 7C). For cnidarians, the region of maximum BGF frequency values occurred north of João Pessoa, Paraíba (Fig. 7D). Mollusks presented an average of 21% of BGF concordances spread across a large portion of the Brazilian coast, from latitude 04° 50’ S to 25° 24’ S, corresponding to Region II in the total dataset results (Fig. 5). Cnidarians also presented a Region II-like distribution between latitudes 10° S and 20° S. Interestingly, results from all four taxa showed a region of BGFgam minima (Figs. 5A-D) that tends to coincided with the minima observed in the total evidence gam between latitudes 20° S and 25° S (= Region III in Fig. 5). This region of BGF frequency minima was always followed by an increase in BGF frequency farther south (Region IV), passing 25° S latitude and generally peaking at Cape Santa Marta (28° 36’ S).