Phylogenetic signal and climatic niche of stem photosynthesis in the mediterranean and desert regions of California and Baja California Peninsula

Abstract

PREMISE Woody plants with photosynthetic stems are common in the drylands of the world; however, we know little about the origin(s) and geographical distribution of photosynthetic stems. Therefore, we set to answer the following questions: (1) Is stem photosynthesis phylogenetically conserved? (2) Do green‐stemmed and fleshy‐stemmed species have identifiable climatic niches? METHODS We mapped the photosynthetic stem trait onto a phylogeny of 228 mediterranean and desert species and calculated indices of phylogenetic signal and created climatic niche models of 28 species belonging to three groups: green, fleshy, and green‐and‐fleshy stemmed species. RESULTS We found phylogenetic signal in the fleshy stem trait, but not in the green stem trait. Fleshy‐stemmed species occupy areas associated with high isothermality, high precipitation seasonality, and high mean temperature of the wettest quarter, whereas green‐stemmed species occupy areas associated with high precipitation of driest month, high precipitation of coldest quarter, high mean diurnal temperature range and high maximum temperature of the warmest month. CONCLUSIONS Despite the fact that both photosynthetic stem types help cope with water shortage, having fleshy stems allows plants to cope with greater precipitation seasonality than is possible with green stems. Green stems require a lot of water to be stored in the soil to maintain net photosynthesis during the dry season, so they inhabit areas with higher and more predictable precipitation.

Implications of barrier ephemerality in geogenomic research

“…It may be that peninsulas and linear coastlines are particularly conducive for this phenomenon. Second, divergence is amplified under differential selection for low‐dispersing species; along the arid Baja peninsula, there is a strong gradient in the annual amount and seasonality of precipitation (Avila‐Lovera & Garcillán, 2021; Cab‐Sulub & Álvarez‐Castañeda, 2021), both controlled by the North American monsoon (Adams & Comrie, 1997; Higgins et al, 1999), which suggests differential adaptation may also be an important factor for interpreting this signal (Klimova et al, 2018). Importantly, species do not have the same physiology and niche constraints and therefore are not expected to be equally impacted by this gradient.…”

A high stem to leaf ratio reduced rainfall use efficiency under altered rainfall patterns in a semi‐arid grassland in northeast China

“…Moreover, while stems are also capable of photosynthesis via two photosynthetic pathways (SNP: stem net photosynthesis; SRP: stem recycling photosynthesis) (Ávila‐Lovera et al . 2014, Ávila‐Lovera and Garcillán 2020, Roo et al . 2020), water loss from stems is significantly less than from leaves.…”

“…2020), water loss from stems is significantly less than from leaves. Plants that utilize SNP are characterized by having stomata in the stem epidermis (Ávila‐Lovera and Garcillán 2020), but the number of stomata on plant stems is significantly lower than on the abaxial surface of the leaves (Ávila‐Lovera et al . 2014).…”

Cell wall polysaccharide and glycoprotein content tracks growth‐form diversity and an aridity gradient in the leaf‐succulent genus Crassula

“…These collapsible cell walls often occur alongside an array of other co‐adaptive traits that make up the succulent syndrome, such as CAM photosynthesis, 3D vascular patterning, and xeromorphic features like low stomatal density and thick waxy cuticles (Males, 2017; Ogburn & Edwards, 2010, 2013; von Willert et al, 1992). The succulent syndrome is not a discrete trait but rather a complex syndrome that ranges from higher to lesser degrees of succulence and its associated traits, a gradation that has often been linked to gradients of aridity and precipitation seasonality (Ávila‐Lovera & Garcillán, 2021; Evans et al, 2014; Frenette‐Dussault et al, 2012).…”