File:Casuarina equisetifolia (ironwood) (Captiva Island, Florida, USA) 4 (15604708497).jpg

Casuarina equisetifolia Linnaeus, 1759 - ironwood (a.k.a. Australian pine) in Florida, USA.

Plants are multicellular, photosynthesizing eucaryotes. Most species occupy terrestrial environments, but they also occur in freshwater and saltwater aquatic environments. The oldest known land plants in the fossil record are Ordovician to Silurian. Land plant body fossils are known in Silurian sedimentary rocks - they are small and simple plants (e.g., Cooksonia). Fossil root traces in paleosol horizons are known in the Ordovician. During the Devonian, the first trees and forests appeared. Earth's initial forestation event occurred during the Middle to Late Paleozoic. Earth's continents have been partly to mostly covered with forests ever since the Late Devonian. Occasional mass extinction events temporarily removed much of Earth's plant ecosystems - this occurred at the Permian-Triassic boundary (251 million years ago) and the Cretaceous-Tertiary boundary (65 million years ago).

The most conspicuous group of living plants is the angiosperms, the flowering plants. They first unambiguously appeared in the fossil record during the Cretaceous. They quickly dominated Earth's terrestrial ecosystems, and have dominated ever since. This domination was due to the evolutionary success of flowers, which are structures that greatly aid angiosperm reproduction.

The woody trees on the left side of the above photo are ironwood/Australian pines (Casuarina equistefolia). The zone of dead vegetation in the foreground and near-center midground represents allelopathic suppression of native plants by the Casuarina trees.

Casuarina is not native to Florida. It occurs naturally in parts of southeastern Asia, Australia, and on many islands in the southwestern Pacific Basin. Ironwood was introduced to the New World a couple centuries ago by the British as windbreaks between adjacent plantations. Casuarina has rapidly invaded many shorelines, beaches, and islands - its seeds are very mobile and indestructible in seawater.

Casaurina shades out low-lying, native, back-beach vegetation. Its root systems are also toxic to native back-beach floras. The green vegetation on the right side of the above photo has not yet succumbed to Casuarina's allelopathic suppression.

Classification: Plantae, Angiospermophyta, Fagales, Casuarinaceae

Locality: Alison Hagerup Beach, western shoreline of Captiva Island, southwestern Florida, USA

Most info. provided by Neil Sealey and James Cheshire.

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