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Compare-Contrast-Connect: Biogeography

NGSS Science and Engineering Practices:

NGSS Disciplinary Core Ideas:

Humans are not the only organisms whose transport has been influenced by currents. One way animals can arrive in new places is by “rafting” or riding the currents and winds to travel across the ocean. It is speculated that this is one of the ways in which different marine larvae arrive in isolated areas like Hawai‘i.

 

Biogeography is the study of the distribution of different species in different regions on the earth. Scientists make hypotheses about the origins of the different kinds of plants and animals in a location based on their biogeography. Biogeography is very important in trying to determine the origins of the plants and animals that live in isolated locations like the Hawaiian Islands. Biogeographers use current species distribution to examine how marine organisms have used ocean currents to move over time.

 

Many marine organisms, such as corals, rely on currents to disperse their larvae in the ocean. For most corals the larval stage is the only time that they are able to move around and find a suitable place to start a new coral colony. Ocean currents play an important role in dispersing marine larvae, and occurrence of some species can be correlated with prevailing ocean currents in the area. SF Table 3.1 shows examples of marine organisms whose larvae are dispersed by oceanic currents, but who only occupy certain areas of the Pacific. Some species are found in certain locations, but not others, even though they have a similar climate and water temperature. Their biological distribution is dependent on oceanic currents and helps scientists understand past current movement as well as future biological distribution.

 

SF Table 3.1. Occurrence of selected marine species across the Pacific ocean basin.
Location Hawai‘i Japan Australia California Baja Philippines
Fish Saddle wrasse       Saddle wrasse
  Fourspot butterflyfish Fourspot butterflyfish     Fourspot butterflyfish
  Moorish idol Moorish idol Moorish idol Moorish idol Moorish idol
  Hawaiian Sergeant       Hawaiian Sergeant
  Flame angelfish Flame angelfish Flame angelfish   Flame angelfish
Corals Lobe coral Lobe coral Lobe coral   Lobe coral
  Rice coral Rice coral Rice coral   Rice coral
    Staghorn coral Staghorn coral   Staghorn coral
  Solitary mushroom coral Solitary mushroom coral Solitary mushroom coral   Solitary mushroom coral
Other invertebrates Crown-of-thorns sea star Crown-of-thorns sea star Crown-of-thorns sea star   Crown-of-thorns sea star
  Day octopus   Day octopus   Day octopus
  Triton's trumpet snail Triton's trumpet snail Triton's trumpet snail   Triton's trumpet snail
  Left handed hermit crab       Left handed hermit crab

 

Different marine organisms synchronize their spawning events to take advantage of higher levels of food, predator avoidance, and preferred water temperatures that are associated with ocean currents. As shown in SF Fig. 3.5, selected marine species across the Pacific ocean basin produce larvae that rely on currents for movement. For example, rice coral will spawn in Hawaii during summer months, and their spawning occurs during a 1–3 day window, within a 1–2 hour time frame. Rice coral uses water temperature and moon irradiance to synchronize its spawning with that of other coral colonies of the same species. Other marine species such as fireworms and fish have synchronized their spawning releases with rice coral in order to avoid predators that feed on gametes in the water column, increasing survival chances for their offspring. In years when ocean currents are disrupted, the number of surviving larval fish is typically lower. A disruption in oceanic currents can cause fluctuations in temperature that can cause coral spawning to fail, disrupting the gamete release of other organisms. The biogeography of an organism may be affected if disruption of the current persists, leading to new areas of distribution, or populations that are reproductively isolated.

<p><strong>SF Fig. 3.5.</strong> (<strong>A</strong>) Moorish idol fish (<em>Zanclus cornutus</em>)</p><br />
<p><strong>SF Fig. 3.5.</strong>&nbsp;(<strong>B</strong>) Mushroom coral (<em>Fungia</em> sp.)</p><br />
<p><strong>SF Fig. 3.5.</strong> (<strong>C</strong>) Crown-of-thorns sea star (<em>Acanthaster planci</em>)</p><br />


 

Question Set: 
  1. Examine SF Table 3.1 and SF Fig. 3.5. Compare the list of marine species found in Hawai‘i with those found in other locations around the Pacific ocean basin.
    1. Which location has a collection of fish species most similar to Hawai‘i’s?
    2. Which location has the least species in common with Hawai‘i?
    3. From which regions in the Pacific ocean basin might you suspect Hawai‘i’s species to originate?
       
  2. Islands are particularly interesting to biogeographers because they tend to have unique assemblages of organisms that have arrived over time from other locations. Only a single land mammal species (the Hawaiian hoary bat) occurs naturally in the Hawaiian Islands. How might you explain this fact?
     
  3. Baja California has many different types of corals, but none of the three species that are distributed throughout the Pacific ocean. Using your knowledge of oceanic currents, explain why you think Baja California does not have the three coral species that are listed in SF Table 3.1.

Special Feature Type:

Exploring Our Fluid Earth, a product of the Curriculum Research & Development Group (CRDG), College of Education. University of Hawaii, 2011. This document may be freely reproduced and distributed for non-profit educational purposes.