In this work, we investigated the chromosome number and genome size of two Mediterranean Amaranthaceae species, namely Atriplex mollis from southern Tunisia and A. lanfrancoi (formerly Cremnophyton lanfrancoi) from Malta. The two species were found to be diploid (2n=18) for all examined populations. This result is different from that previously reported for Cremnophyton lanfrancoi Brullo and Pavone (2n=20). Genome size showed that both species have a close mean amount with 2C=3.41 and 3.51 pg, respectively. Two groups were distinguished with regard to genome size (P<0.01). It should, however, be noted that the majority of populations, with the exception of those from Djerba and Chbika, may be intermediate between the two basic groups. Moreover, the difference does not appear to depend on geographical distribution and environmental aspects. It would rather depend on chromosome rearrangements. The morphological similarities, the monophyly of Atriplex including A. lanfrancoi, previously ranked in genus Cremnophyton, sharing the same chromosome number and the same genome size, support the placement of Cremnophyton within the genus Atriplex.

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This study was supported by the ERANETMED2-72-303 PACTORES project financed by the Ministry of Higher Education and Scientific Research of Tunisia and University of Malta (Argotti Botanic Gardens) and by projects 2017SGR1116 (Catalan government) and CGL2017-84297-R (Spanish government).

Artículo de 8 páginas que incorpora como material gráfico mapas de localización geográfica, tablas e imágenes de microscopio con cromosomas evidenciados.