17th Annual Conference of the Ecological Society of Germany, Switzerland and Austria -
Section Plant Population Biology, May 2004 in Regensburg/Germany:
Population dynamics in a changing landscape - persistence, dispersal or adaption?

Spatial and temporal population dynamics and morphology of a violet hybrid in polluted pine forests of the Dübener Heide (Saxony-Anhalt)

Friederike Erlinghagen
UFZ Centre for Environmental Research Leipzig-Halle, Department of Community Ecology
Theodor-Lieser-Straße 4, D-06120 Halle, Germany

Correspondence: F. Erlinghagen, Wilhelm-Raabe-Weg 6, D-30938 Burgwedel, Germany

E-Mail: infoogzpLw@friederike-erlinghagen.de

Abstract

(Please click here for complete results of the investigations)

The investigations were focused on the demography and morphology of the clonal perennial hybrid Viola riviniana RCHB. x Viola reichenbachiana JORDAN ex BOR. (V. x intermedia RCHB., V. x bavarica SCHRANK) in central Germany . In particular, the aims of the study were to investigate quantitatively the importance of sexual and clonal propagation with regard to the local dynamics of the hybrid and to evaluate the consequences of propagation patterns and morphological characters on adaptation to the changed environment of polluted pine forests. 

The demographic study was carried out in six violet populations of different ages under different habitat conditions: young spreading populations of the hybrid in polluted pine forest sites and old established populations of Viola riviniana in an isolated deciduous forest site were compared. A number of differences were identified with regard to seedling recruitment between the pine forest sites and the deciduous forest sites. In both of the latter, evidence was found for repeated seedling recruitment in addition to clonal growth in Viola populations. The results indicate that clonal propagation is accompanied by high ramet mortality (high annual turnover). In pine forest populations seedling germination is partly a result of seed limitation, whereby singly-accumulated and early germination leads to density-dependent mortality. Here, the seed weight seems to play an important role for survival and competitiveness. The weaker correlation between seedling recruitment and fruit production as well as positive density-dependency indicate that the variation in microsite quality is more important for older populations in deciduous forest sites. The established and isolated populations in deciduous forest sites produce seeds that are significantly lighter than those of pine forest populations. As a consequence, their resources are fewer, which makes their germination and establishment far more dependent on varying microsite quality. As a consequence of abortion and “genetic load” it may additionally be concluded that seeds are more adapted in these microsites. 

Despite genetic and demographic differentiation, the investigations indicate a number of mutual characteristics between all violet populations: resource allocation capability and the resulting high costs of reproduction lead to a short ramet life span, thus raising the question of an optimum life-history strategy. Both the present demographic studies as well as the molecular-genetic investigations of Neuffer et al. 1999 lead to the hypothesis that introgressive hybridization results in novel genotypes adapted to the changed environment of polluted pine forests. It will be assumed that the Viola populations of the pine forests have “colonized their respective sites during the past few centuries” (in citing Neuffer et al. 1999). But the results raises the question of the introgressive hybridization of Viola species described to aerial pollutions occurred not until the last decennia. Viola riviniana and Viola reichenbachiana coexist in the isolated deciduous forest sites within the pine forests of the Dübener Heide, so that from this hybridization and invasion is possible. 

Keywords: Clonal growth, environmental pollution, introgressive hybridization, seedling recruitment, trade-off, Viola riviniana

References

Auge H., Neuffer B., Erlinghagen F., Grupe R., Brandl R. 2001
Demographic and random amplified polymorphic DNA analyses reveal high levels of genetic diversity in a clonal violet. Molecular Ecology, 10, 1811-1819. 

Erlinghagen F. 1995. Populationsökologische Untersuchungen an Viola riviniana RCHB. In unterschiedlich stark geschädigten Kiefernforsten der Dübener Heide (Sachsen-Anhalt). Kieler Notizen, 23, 16-19. 

Erlinghagen F. 1998. Populationsökologische Untersuchungen an Viola riviniana RCHB. In immissionsgeschädigten Kiefernforsten der Dübener Heide (Sachsen-Anhalt). Unpublished manuscript, pp. 90.

Neuffer B., Auge H., Mesch H., Amarell U., Brandl R. 1999
Spread of violets in polluted pine forests: morphological and molecular evidence for the ecological importance of interspecific hybridization. Molecular Ecology, 8, 365-377.

Interesting continued literature: Maron, J.L, Vila, M., Bommarco, R., Elmendorf, S., Beardsley, P. (2004)
Rapid evolution of an invasive plant. Ecological Monographs, 74(2), pp.
261-280.