The gymnosperms are often called ‘Living Fossils’, or are dismissed as being primitive. Gymnosperms are indeed ancient: originating in the carboniferous period (Bowe, Coat, & dePamphilis, 2000). They can be divided into four monophyletic groups: ginkophytes, gnetophytes, cycads, and the largest of the four (with more than 600 extant species), conifers. Conifers account for the greatest diversity amongst the gymnosperms. This diversity might pale in comparison to that of the angiosperms, but a group can have biological importance without being speciose. From an ecological point of view, gymnosperm success is in fact comparable to angiosperms, as gymnosperms are thriving in important niches across latitudes. This is …show more content…
Though specific geographical distributions of gymnosperms are poorly documented, some broad conclusions have been made. For instance, Bond (1989), Coomes et al. (2005), and Lusk (2011) found that competition with angiosperms has limited all living gymnosperms to areas of high latitude and high elevation. This has also been documented in a recent meta-analysis by Fragniere et al. (2015). Gymnosperms hence exhibit the inverse of the general latitudinal diversity gradient: in species richness from the equator to the poles, and decreasing at equatorial latitudes. The observed pattern is apparent when considering gymnosperms as a group and when the group is split into separate lineages. One downfall of their analysis is, however, that the varying availability of land approaching the equator was not taken into account, which would perhaps be a confounding factor. While this needs to be corrected for, the study nevertheless pinpoints an underlying pattern that would likely be retained when standardized by land area available.
Despite the species richness of gymnosperms decreasing as latitudes tend toward the equator, Fragniere et al. (2015) reported that half of all gymnosperms can, in fact, be found between the tropics (the main results of their paper are summarised in box 2). These …show more content…
In Waring and Franklin’s (1979) classic study, an explanation is put forth as to why large, old conifers dominate the Pacific Northwest forests (summarised in box 3). Specifically, their large size, longevity, leaf shape and carbon balance are considered adaptive advantages. Though the evergreen forests are unique, the conclusions tend to be applicable to other conifer forests – for instance those in Japan and New Zealand (Pacala, et al., 1996).
Additionally, in north temperate ecosystems, Pinaceae are aggressive competitors (Brodribb, Pitterman, & Coomes, 2012). As in Waring and Franklin’s (1979), the Pinaceae’s needle-like leaves, which are tightly packed, protect their vascular tissue and thus allow for a high photosynthetic efficiency and for photosynthetic rates equal or superior to analogous angiosperms. This, in addition to their freeze-thaw resistant vascular systems (Brodribb & Feild, 2008) allow them to disperse across the northern hemisphere (Fragniere, Betrisey, Cardinaux, Stoffel, & Kozlowski, 2015). Similarly, in areas of low temperature and nutrients, Podocarps are able to outperform angiosperms, as their efficient nutrient use allows for survival on lowland soils (Brodribb, Pitterman, & Coomes, 2012). They have also been found to be competitive in tropical forests: