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Cedrela lilloi C. DC. (cedro coya, Meliaceae), an important south American timber species, has been historically overexploited through selective logging in Argentine Yungas Rainforest. Management and conservation programs of the species require knowledge of its genetic variation patterns; however, no information is available. Molecular genetic variability of the species was characterized to identify high-priority populations for conservation and domestication purposes. Fourteen native populations (160 individuals) along a latitudinal gradient and with different logging's intensities were assessed by 293 polymorphic AFLP (amplified fragment length polymorphism) markers. Genetic diversity was low (Ht = 0.135), according to marginal location of the species in Argentina. Most of the diversity was distributed within populations (87%). Northern populations showed significant higher genetic diversity (R2= 0.69) that agreed with latitudinal pattern of distribution of taxonomic diversity in the Yungas. Three clusters were identified by Bayesian analysis in correspondence with northern, central, and southern Yungas. An analysis of molecular variance (AMOVA) revealed significant genetic differences among latitudinal clusters even when logging (ΦRT = 0.07) and unlogging populations (ΦPT = 0.10) were separately analyzed. Loss of genetic diversity with increasing logging intensity was observed between neighboring populations with different disturbance (ΦPT = 0.03–0.10). Bottlenecks in disturbed populations are suggested as the main cause. Our results emphasize both: the necessity of maintaining the genetic diversity in protected areas that appear as possible long-term refuges of the species; and to rescue for the national system of protected areas some high genetic diversity populations that are on private fields.

Key message Genetic variability of Araucaria angustifolia populations in Argentina was moderate-to-low and reduced by logging. Some studied populations and the plantation are valuable gene pools for conservation and management. Abstract The main forces shaping genetic variability of woody species in fragmented forest are the geographical distribution and demographic history of populations. We conducted molecular analyses to evaluate how these factors have affected Araucaria angustifolia genetic variability in the Argentinean Parana Forest and to identify valuable gene pools for conservation and management purposes. Using 706 polymorphic AFLP (Amplified Fragment Length Polymorphism) markers, we analyzed nine native populations with different logging history and one plantation (312 individuals) of an uncertain origin. Average genetic diversity for the native populations was moderate-to-low (He = 0.128) in accordance with their marginal location within Araucaria's range. In general, genetic diversity of populations decreases from east to west with increasing distances from the main area of species distribution on southern Brazil. Logging may have been responsible for further reduction of genetic variability in the more intensely exploited populations of the southern region and in some private fields. The moderate genetic differentiation among populations (Φ PT = 0.080) suggests an increase in the genetic structure of remnant populations because of fragmentation. UPGMA and Bayesian analyses agreed with the geographic location of populations. Populations from the southern Provincial Parks at Araucaria's range edges grouped and differed genetically more from other populations. The highest genetic diversity of the plantation (He = 0.155) suggests that its individuals could have originated from seeds collected from different and/or highly variable sources of Brazil and the northeast of Argentina.

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The effects of different simulated rainfall regimes on water relations, growth, and biomass production and allocation of five provenances of Cedrela fissilis, C. saltensis and C. balansae were assessed in a pot-grown seedling experiment in greenhouse under uncontrolled conditions. Four simulated rainfall regimes were applied: 600 mm year -1 (severe water deficit), 800 mm year -1 (mild water deficit), 1,000 mm year -1 (mild wet), and 1,200 mm year -1 (well-watered) used as control. Provenances were compared in terms of water relations (midday leaf water potential, W md and relative water content, RWC), growth (root, shoot and leaf length, neck diameter), growth rate (shoot-and neck growth rate, SGR and NGR), biomass production (root, shoot and leaf dry weight), and biomass allocation (root:shoot ratio, RSR). Multivariate analyses revealed that water relations differed significantly under all simulated rainfall treatments by means of several variables throughout time. Effects of species 9 treatment, and provenance nested within species 9 treatment interactions significantly were important. SGR and RSR also were important to explain differences in W md and RWC between treatments and provenances. Broadly C. balansae and C. saltensis provenances seem to display a better performance than C. fissilis provenances under severe water deficit only. However, despite differences between provenances, it was not possible to clearly separate them according to their origin, based on water relations and growth performance. Even though the results of this study performed on pot-grown seedlings are based on relatively few observations and require additional confirmation, they allow an opportunity for speculation on the factors that are related to intraspecific variations that are likely to occur during the growth of seedlings from different geographical sites in field condition.