Seasonal controlling factors of CO2 exchange in a semiarid shrubland in the Chihuahuan Desert, Mexico.

The still significant uncertainties associated with the future capacity of terrestrial systems to mitigate climate change are linked to the lack of knowledge of the biotic and abiotic processes that regulate CO2 net ecosystem exchange (NEE) in space/time. Mainly, rates and controls of CO2 exchange from arid ecosystems, despite dominating the global trends in interannual variability of the terrestrial CO2 sink capacity, are probably the most poorly understood of all. We present a study on rates and controls of CO2 exchange measured with the eddy covariance (EC) technique in the Chihuahuan Desert in the Northeast of Mexico, to understand how the environmental controls of the NEE switch throughout the year using a multilevel approach. Since this is a water-limited ecosystem, the hydroecological year, based on the last precipitation and the decay of air temperature, was used to compare the wet (from May 16 to October 30, 2019) and dry (November 1, 2019 to May 15, 2020) seasons' controlling mechanisms, both at diurnal and nocturnal times. Annual NEE was -303.5 g C m-2, with a cumulative Reco of 537.7 g C m-2 and GPP of 841.3 g C m-2. NEE showed radiation, temperature, and soil moisture sensitivity along the day, however, shifts in these controls along the year and between seasons were identified. The winter precipitations during the dry season led to fast C release followed by lagged C uptake. Despite this flux pulse, the ecosystem was a net sink throughout most of the year because the local vegetation is well adapted to grow and uptake C under these arid conditions, even during the dry season. Understanding the controls of the sink-source shifts is relevant since the predictions for future climate include changes in the precipitation patterns.

A new species of the genus Phonotimpus Gertsch amp; Davis (Araneae: Phrurolithidae) from Mexico and the transfer of Gosiphrurus schulzefenai Chamberlin amp; Ivie to Phonotimpus.

Phonotimpus padillai sp. nov. is described on the basis of morphological characteristics of both sexes: males are easily distinguished by the shape of the embolus and females by the shape of the copulatory openings. Additionally, Gosiphrurus schulzefenai Chamberlin Ivie, 1936 is transferred to the genus Phonotimpus Gertsch Davis, 1940, based on the redescription of the female and first description of the male, with an update of the diagnosis of this species.

Four new species of the genus Novalena Chamberlin amp; Ivie, 1942 (Araneae: Agelenidae) from southeastern Mexican montane forests and first record of ocular anomaly in the genus.

Four new species of the spider genus Novalena Chamberlin Ivie, 1942 are described: N. bola sp. nov., N. mayae sp. nov., N. padillai sp. nov., and N. zootaxa sp. nov. All species were collected in montane forests in Chiapas, Mexico, and three of them occur in sympatry across their distribution range.

Diversity and seasonal variation of ground and understory spiders from a tropical mountain cloud forest.

We made intensive samplings to study the seasonal response of spiders across different forest strata (ground and understory) in a tropical mountain cloud forest from Mexico. We sampled spiders from ten plots in six sampling events during the dry and rainy season, to analyze their abundance, structure (distribution of abundance among species), diversity and the response of the five dominant species at each stratum. Results demonstrated that seasonal patterns of spider communities differed among strata, revealing a complex spatiotemporal dynamic. Abundance, structure, diversity of ground spiders, as well as the responses of four dominant species at this stratum, showed low seasonal variations. In contrast, a strong seasonal variation was observed for the understory assemblage, with lowest abundance and highest diversity in the rainy season, and different assemblage structures for each season. Seasonal patterns of each assemblage seem linked to the responses of their dominant species. We found high co-occurrence among most of the ground dominant species with similar habitat use and with multivoltine patterns, contrasting with low co-occurrence among most of the understory dominant species with similar habitat use and univoltine patterns. Our results showed that the spiders' assemblages of tropical mountain cloud forest (opposed to what is found in temperate and boreal forests) increase their species richness with the height, and that their responses to seasonal change differ between strata. Management programs of these habitats should consider the spatial and temporal variations found here, as a better understanding of their ecological dynamics is required to support their sustainable management.

A new species of the spider genus Wirada (Araneae, Theridiidae) from Mexico, with taxonomic notes on the genus and a key to the species.

Wirada Keyserling, 1886 is one of the smallest genera of Theridiidae with only five South American species (World Spider Catalog 2018). Keyserling (1886) described first Wirada punctata (male) from Peru. Simon (1895) described W. rugithorax and W. tovarensis (males) from Venezuela, but Levi (1963) synonymized W. rugithorax with W. punctata. Later, Levi (1967) described W. tijuca (male) from southeastern Brazil, and lately Lise et al. (2009) described W. sigillata Lise, Silva Bertocello, 2009 and W. araucaria Lise, Silva Bertocello, 2009 (males and females) from southern Brazil. Simon (1894) placed Wirada in its group Histogonieae, and stated it is close to Pholcommateae. Until now, none species of Wirada has been included in any phylogenetic study of Theridiidae, only Agnarsson (2004) when commented the Pholcommatinae said "Based on the synapomorphies of the group it is likely that ... Wirada belong to this subfamily." Recently, this genus was reported (as Wirada sp1) from two localities in Mexico (Ibarra et al. 2011; Álvarez-Padilla 2015; Rivera-Quiroz et al. 2016) and subsequent samplings on three other sites from Chiapas (Campuzano et al. 2016) exposed more specimens. After examining these specimens, we found they do not match any of the known species and therefore we propose a new species. We also include taxonomic and biological notes about the genus and a key to the species.