Table 2

Divergence time estimates among seahorse lineages whose cladogenesis may have been the result of vicariance events by virtue of the present-day distribution patterns of their species.

Node


Calibration range

B

C

D

E

F

G


3.1 – 3.5

3.73 ± 0.29

3.67 ± 0.42

15.12 ± 3.46

1.47 ± 0.53

5.33 ± 1.79

14.60 ± 3.37

(2.26 – 5.84)

(3.18 – 4.76)

(9.85 – 23.26)

(0.54 – 2.61)

(2.64 – 9.47)

(9.53 – 22.49)

3.1 – 4.6

4.26 ± 1.15

4.16 ± 0.66

16.60 ± 4.00

1.66 ± 0.63

6.01 ± 2.13

16.05 ± 3.89

(2.46 – 6.94)

(3.24 – 5.70)

(10.50 – 26.05)

(0.60 ± 3.04)

(2.89 – 11.14)

(10.09 – 25.22)

3.1 – 8.5

5.15 ± 1.92

5.03 ± 1.50

19.07 ± 5.76

2.02 ± 0.94

7.18 ± 3.07

18.46 ± 5.63

(2.60 – 9.98)

(3.27 – 8.75)

(11.04 – 33.05)

(0.66 – 4.31)

(3.07 – 14.87)

(10.60 – 32.16)


Divergence times were estimated using the program MULTIDIVTIME [102] under the assumption that the closure of the Central American Seaway (Node A in Fig. 2) resulted in the divergence of two sister lineages associated with the eastern/central Pacific (Hippocampus ingens and H. fisheri) and Atlantic Oceans (H. reidi and H. algiricus), respectively. Phylogeographic distribution patterns may have been the result of the following vicariance events. Node B (Indian Ocean vs. West Pacific): Closure of the Indonesian Seaway. Nodes C and D (Indo-Pacific vs. Atlantic Ocean): Closure of the Tethyan Seaway. Node E, F and G (amphi-Atlantic distribution patterns): continental break-up and spreading of the Atlantic Ocean. Three possible calibration ranges for the closure of the Central American Seaway were specified. Comparisons of the species affected by this vicariance event with other teleosts having similar distribution patterns (Fig. 3) indicate that the seahorses were among the last to diverge. This suggests that their cladogenesis was associated with the final closure of the seaway, i.e. no earlier than approximately 4.6 mya (a hypothesis that is further supported by the finding that marine organisms in nearshore habitats were among the last species to have diverged as a result of Central American seaway closure [20,60,61]). Divergence time estimates are indicated as mean ± S.D. (95% confidence interval). Suggested dates of vicariance events: Central American Seaway closure: 3.1 – 3.5 mya (assuming that the divergence of the transisthmian seahorse lineages took place when a land bridge formed in Central America [18]); 3.1 – 4.6 (taking into consideration that seahorse divergence may have been affected by the reorganisation of ocean currents associated with the closure of the seaway [24]); 3.1 – 8.5 mya (the upper bound being the time when the earliest recorded evolution associated with the closure of the seaway took place in marine corals and foraminiferans [25]); Indonesian Seaway closure: 0.01 – 1.8 [47,48]; 3 – 4 mya [46]; 7 – 10 mya [44,45]; 15 – 17 mya [43]; Tethyan Seaway closure: 11.2 – 14.8 mya [34,35]; 18.4 – 20.5 [36]; 23.8 – 28.5 [31]; complete separation of the land masses on either side of the Atlantic Ocean: 84 mya [50].

Teske et al. BMC Evolutionary Biology 2007 7:138   doi:10.1186/1471-2148-7-138

Open Data