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).