Genecologcal differentiation in Leptospermum flavescens Sm. in the Sydney region

Abstract

Evidence is presented for the existence of two genecoiogically differentiated groups in Leptospermum flavescens in the Sydney region. A morphologicai study of 18 attributes of herbarium specimens indicates three groups of plants: one small-leaved, one large-leaved and one intermediate. Comparative cultivation under standard conditions and seed germination experiments indicate only two discrete groups, because the intermediate group behaves similarly to the large-leaved group. Correlation of population distribution with soil nutrient status suggests that organ size in the large-leaved group is phenotypically plastic in relation to low soil nutrients. This is confirmed by comparative cultivation under high and low nutrient regimes. Reciprocal transplanting of cuttings on a small scale suggests that the two groups are intolerant of each other's habitats.

Altitudinal variation in Leptospermum flavescens Sm. (Myrtaceae)

“…These data came from either the herbarium labels or the New South Wales 1 ; 25 000 or I : 50 000 Topographic Maps, Nonparametric Spearman rank correlations (Zar 1974) were then carried out on the altitudinal scale and a set of 11 morphological attributes measuring average flower, fruit and leaf size (Table 1), For the analyses, the specimens were separated into the two genotypic groups recognized by Morrison and Myerscough (1982): large-leaved (average leaf length > 22 mm) and small-leaved (average leaf length < 20 mm).…”

“…In fact, the large-leaved specimens have a significantly reduced leaf length at higher altitudes. This altitudinal convergence does not correlate with differences in soil parent material [as quantified by Morrison and Myerscough (1982)] (Table 1), and so the variation is presumably independent of this factor.…”

“…However, this arrangement proved to be unsatisfactory when the mountain populations were taken into account (cf. Beadle et al 1982), In their experimental analysis of variation in these taxa, Morrison and Myerscough (1982) A re-analysis of their data to incorporate altitude as a factor thus allows an assessment to be made of the degree to which the altitudinal variation in morphology is genetically fixed in the populations.…”

“…Leptospermum flavescens Sm, sensu lato is a highly variable species endemic to New South Wales, including Lord Howe Island, and Queensland (Morrison & Myerscough 1982), In the area south of Sydney, two distinct taxa have been recognized in the past (e,g. Bentham 1866;Cheel 1921;Beadle e/ al.…”

“…These two taxa have recently been shown to be genecologically differentiated: there are two distinct groups of genotypes, but the plants with larger flowers and leaves show phenotypic reduction in leaf size in response to lower nutrient levels in the substrate (Morrison & Myerscough 1982), The considerable morphological intergradation which exists between these taxa cannot, however, all be attributed to variation in soil fertility. This note presents evidence that much of the apparent intergradation between these taxa is due to altitudinal variation in morphology which is genetically fixed within the populations.…”