Angela Dhungana
S. Annette Shelton
BIOL 1615
07/19/2013
Summary: Rear Species Support Vulnerable Functions in High Diversity Ecosystems
Biologically rich environments include a large number of rare species, in other words, species
that are uncommon and are in danger of extinction. Generally, the functional contribution of
these rare species are considered to have little or no impact in the functioning of the ecosystem
compared with other common species. However, a new study published 28 May in the Journal
PLOS Biology denies this idea about rare species.
The rare species increase the functioning diversity in the eco-system. The rare species exhibit
functional traits different from that of common species. During normal environmental
conditions, common species are enough to help maintain the ecosystem. But the adverse
environmental conditions results in ineffectiveness of those common functions. During worst
environmental conditions, rare species function actively that help protect the ecosystem. Thus,
the assumption of rare species offering only the “ecological insurance” when common species
die out has been denied.
The group of researchers working to address the importance of rare species falsified the
assumption using three different ecosystems including coral reefs, alpine meadows and tropical
forests. The data was estimated referencing the rarity of species at two levels.
1. Local level
2. Regional level
For both the local and regional level, the researchers defined ‘rare’ species as those with a local
abundance less than 5% of the most common species and the rarest species as those represented
by a single individual having one occurrence or less than 1% of the most common species. On
the basis of these references, the researchers proposed functional indistinctiveness model. The
species in both the local and regional level for three different ecosystems, coral reef, alpine
meadows and tropical forests, were measured on a standardized scale. The researchers compared
the species among the ecosystems and those comparisons led them to a conclusion that the
distinguishing trait of the rare species were inversely related to the traits of common species.
For the Reef fishes and the tropical tress, the rare species supported the highly peculiar function
and the common species supported the least peculiar function. For alpine plants, there were only
two species showing high peculiarity including Saxifraga mutate and Rosa sempervirens. The
researchers also proposed a vulnerability model for each of the Reef fish, Alpine plants and the
tropical trees. The model was prepared on the basis of the commonness showed by the species.
According to the model, the most vulnerable functions, functions distinct from that of common
species, were supported by the rare species that help protect the ecosystem during adverse
environmental conditions.
The Reef fish were sampled along 50 m underwater and 1,390,000 individual fishes and 846
species of fishes were recorded. For the alpine plants, 2979 species were sampled and also the
researchers gathered information from National Alpine Botanical Conservation. For tropical
trees, each tree representing the larger number of species were sampled. A total of 662 species,
217 genera and 56 families were sampled.
The results highlights that it is crucial to protect rare species at both the local and regional level.
Protection in local level helps sustain the local ecosystem process increasing diversity within
communities ultimately resulting in regional diversity. Represented by few individuals, rare
species are generally considered to have minor influence in the ecosystem. Indeed, it is assumed
that the rare species have the same ecological roles as those of common species but less impact
because of their small number, a phenomenon known as functional redundancy. This redundancy
suggests that rare species merely serve as an insurance policy for the ecosystem in case of any
ecological loss. The researchers observed at least one individual from each ecosystem and were
acknowledged that the unique functions were carried out only by rare species.
For coral reef, the researchers observed the 5th most vulnerably functional, the giant moray eel
(Gymnothorax javanicus) and the 20th most vulnerable functional batfish (Platax pinnatus). The
giant moray eel is a predatory fish that feeds at night on fish and invertebrates in the coral reef.
These prey are inaccessible to the predators. Thus, the giant moray eel hunts these invertebrates
and fish balancing their population ultimately resulting the balance in the ecosystem. Similarly,
the bat fish from the coral reef works as a macro algae- a role that many common herbivores of
the coral reef cannot play, and handle temperature and environmental changes making it ideal for
other common species.
For alpine plants, they observed the 3rd most vulnerably functional, the Pyramidal Saxifrage
(Saxifraga cotyledon) and the 5th most vulnerably functional Cytisus polytrichus. Saxifrage
plants have thick and dense leaves and they also tend to live longer. Such long life span gives the
plants enough time to grow and adapt the highly stressful environments. With its long flowering
stems, it serves as an excellent resource for the pollinators. Cytisus polytrichus are developed
from the seeds dispersed by the ants. These seeds are not only dispersed at short distances but are
also buried underground by the ants. Thus, these seeds are adapted from the beginning to avoid
adverse environmental effects which can serve a vital function in the ecosystem.
Among the tropical trees, the researchers observed the highest vulnerably functional Pouteria
maxima (Sapotaceae) which grows more than 40 m in height and at least 75 cm in diameter. This
tree being huge and having thick and dense leaves is remarkably resistant to the fire and drought.
This protects the forest from drying out and also helps prevent the forest fire ultimately leading
to survival of the natural components.
From these observations, the researchers concluded that the rare species serve irreplaceable
functions in the ecosystem. The preservation of the biodiversity as a whole including both the
common and rare species is crucial for the sustenance of ecosystem. Despite their usefulness and
importance in the ecosystem, the rare organisms could disappear as they are supported by
vulnerable species. Their unusual functions help the nature and its component to survive. During
the rapid transitions of the ecosystem, rare species best use their function to save the nature and
to save us. Therefore, it is extremely important to protect such rare species.
Moreover, such rareness and uniqueness is not present abundantly in the nature. The need of
such species and importance of their functions should be realized. They must be protected as it’s
vital for the flexibility and existence of the ecosystem and its varied species.
Works Cited
"Rare Species Support Vulnerable Functions in High-Diversity Ecosystems." PLOS Biology:
N.P., n.d. Web. 19 July 2013.
Public Library of Science. "Rare species perform unique roles, even in diverse ecosystems."
ScienceDaily, 28 May 2013. Web. 19 Jul. 2013.