which varies regionally from less than 1.3 m to more than 3 m per year, with
rainfall on the Caribbean side typically being heavier than on the Pacific side of the
continental divide (Meditz and Hanratty 1987).
The formation of the Isthmus of Panama is considered to be one of the most
important geologic events of the past 60 million years as it had an enormous
impact on Earth’s climate and environment. It occurred due to the gradual collision
of the Pacific, Cocos, Nazca and Caribbean plates which led to uplift of the sea
floor and the formation of volcanic islands. Over the next 12 million years vast
quantities of sediment from North and South America were deposited in between
the newly emerging islands, with final closure of the straits occurring in the late
Pliocene, 2.8 million years ago (mya) (Coates et al. 2005). This formation blocked
the North Equatorial Current which had previously flowed westward through the
Central American Seaway and forced the current northwards forming the Gulf
Stream of today (Berggren and Hollister 1974; Burton et al. 1997). With the
Pacific and Atlantic no longer mixing, there were significant changes in temperature, salinity and primary productivity. This resulted in both species extinctions
and species radiations as environments changed (Jackson et al. 1993). Sister
species that were isolated on either side of the isthmus and that subsequently
diverged are referred to as geminates (Jordan 1908). These represent initially
similar genomes that were isolated and diverged over the last 3 million years
(Lessios 2008) and provide insights into evolutionary adaptations in response to
the changing environments.
Today the Caribbean coast of Panama incorporates coral reefs, seagrass beds,
rocky shores, mud-flats and mangroves and has a narrow continental shelf.
It continues to be influenced by the Atlantic North Equatorial Current which flows
through the Lesser Antilles (Kinder et al. 1985). The coast of the south-western
Caribbean including Panama is also affected by a cyclonic gyre that develops from
this current (Gordon 1967; Kinder et al. 1985; Gómez et al. 2005). For an in-depth
review of the Caribbean habitats of Panama, see Gómez et al. (2005). The
Caribbean experiences very small tidal ranges (less than 0.5 m) and has relatively
stable conditions. Its waters are clear and nutrient poor (D’Croz and Robertson
1997; D’Croz et al. 2005; Collin et al. 2009) and unlike the north coast of
Colombia there is no upwelling. These conditions are suitable for growth of
extensive coral reefs which date back to the early Pleistocene (Glynn 1982; Cortés
1993). Surface waters of the Caribbean have an upper 200 m layer of warm water
heated by solar radiation, which has a correspondingly high salinity. Surface water
temperatures vary from 27 °C in the dry season to 30 °C in the rainy season, while
salinity varies from 36 psu in the dry season to 32 psu in the rainy season (D’Croz
and Robertson 1997). Two archipelagos are present off the Caribbean coast of
Panama, the San Blas (Kuna Yala) Archipelago which has a very narrow continental shelf and is subject to strong ocean influence with an oligotrophic coastal
area (D’Croz and Robertson 1997) and the Bocas del Toro Archipelago, with a
larger continental shelf, and greater influence from continental run-off (D’Croz
et al. 2005). Five national parks have been created along the Caribbean coast of
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S. E. Coppard and J. J. Alvarado
rainfall on the Caribbean side typically being heavier than on the Pacific side of the
continental divide (Meditz and Hanratty 1987).
The formation of the Isthmus of Panama is considered to be one of the most
important geologic events of the past 60 million years as it had an enormous
impact on Earth’s climate and environment. It occurred due to the gradual collision
of the Pacific, Cocos, Nazca and Caribbean plates which led to uplift of the sea
floor and the formation of volcanic islands. Over the next 12 million years vast
quantities of sediment from North and South America were deposited in between
the newly emerging islands, with final closure of the straits occurring in the late
Pliocene, 2.8 million years ago (mya) (Coates et al. 2005). This formation blocked
the North Equatorial Current which had previously flowed westward through the
Central American Seaway and forced the current northwards forming the Gulf
Stream of today (Berggren and Hollister 1974; Burton et al. 1997). With the
Pacific and Atlantic no longer mixing, there were significant changes in temperature, salinity and primary productivity. This resulted in both species extinctions
and species radiations as environments changed (Jackson et al. 1993). Sister
species that were isolated on either side of the isthmus and that subsequently
diverged are referred to as geminates (Jordan 1908). These represent initially
similar genomes that were isolated and diverged over the last 3 million years
(Lessios 2008) and provide insights into evolutionary adaptations in response to
the changing environments.
Today the Caribbean coast of Panama incorporates coral reefs, seagrass beds,
rocky shores, mud-flats and mangroves and has a narrow continental shelf.
It continues to be influenced by the Atlantic North Equatorial Current which flows
through the Lesser Antilles (Kinder et al. 1985). The coast of the south-western
Caribbean including Panama is also affected by a cyclonic gyre that develops from
this current (Gordon 1967; Kinder et al. 1985; Gómez et al. 2005). For an in-depth
review of the Caribbean habitats of Panama, see Gómez et al. (2005). The
Caribbean experiences very small tidal ranges (less than 0.5 m) and has relatively
stable conditions. Its waters are clear and nutrient poor (D’Croz and Robertson
1997; D’Croz et al. 2005; Collin et al. 2009) and unlike the north coast of
Colombia there is no upwelling. These conditions are suitable for growth of
extensive coral reefs which date back to the early Pleistocene (Glynn 1982; Cortés
1993). Surface waters of the Caribbean have an upper 200 m layer of warm water
heated by solar radiation, which has a correspondingly high salinity. Surface water
temperatures vary from 27 °C in the dry season to 30 °C in the rainy season, while
salinity varies from 36 psu in the dry season to 32 psu in the rainy season (D’Croz
and Robertson 1997). Two archipelagos are present off the Caribbean coast of
Panama, the San Blas (Kuna Yala) Archipelago which has a very narrow continental shelf and is subject to strong ocean influence with an oligotrophic coastal
area (D’Croz and Robertson 1997) and the Bocas del Toro Archipelago, with a
larger continental shelf, and greater influence from continental run-off (D’Croz
et al. 2005). Five national parks have been created along the Caribbean coast of
108
S. E. Coppard and J. J. Alvarado