Recent research reveals that Joshua trees, native to the Mojave Desert in the southwestern United States, face significant threats from climate change, despite their remarkable adaptations. To survive the arid environment, these trees developed a specialized process known as Crassulacean Acid Metabolism (CAM) photosynthesis. As temperatures increase and drought extends, their lives are now in jeopardy. The study underscores the urgency to understand how these trees can respond to changing environmental conditions as their existing range diminishes.
Joshua trees, that can live for hundreds of years, are the iconic symbol of the fragile desert ecosystem. They’re up against a dramatically reducing habitat. Some of the trees themselves predate the Industrial Revolution by centuries. Their remarkable longevity is a testament to thriving, often against the odds, in an ever-evolving world. Researchers are exploring the physiological traits and genetic makeup of two species—Yucca brevifolia and Yucca jaegeriana—to assess how they process carbon and nitrogen differently and how these differences may influence their resilience against climate challenges.
The Importance of CAM Photosynthesis
Joshua trees use a special type of photosynthesis called CAM, which enables them to take in carbon dioxide during the cooler nighttime hours. Such an adaptation allows them to save water and still guarantee that when the sun is shining, they’re able to photosynthesize effectively. Scientists have detected the exact genes involved in this uncommon photosynthetic pathway. These genes exhibit expression patterns consistent with anticipated physiological responses.
According to Karolina Heyduk, lead researcher in the study, that’s precisely what makes this finding so important.
“It also helps us confirm the use of CAM photosynthesis. We see, for example, the genes that we know are involved in CAM photosynthesis were expressed at the times we thought they should be, so it’s another way to verify our phenotypes and interrogate why those phenotypes are showing up at all,” – Karolina Heyduk.
Understanding the timing of gene expression in relation to environmental conditions may provide insights into how well Joshua trees can adapt to increasingly harsh climates. Perhaps most exciting about these findings is the potential these trees clearly possess. They’ve been up against an environment that’s becoming more and more inhospitable.
Diminishing Range and Future Challenges
The bad news is that the range of Joshua trees is receding. This drastic decrease is mainly because of increasing heat and prolonged drought, which are products of climate change. This devastating loss of habitat presents dire threats to their survival. Joshua trees cannot reproduce outside their current geographic range, bringing into question the species’ sustainability in the long-term.
“What today’s seedlings are experiencing is going to be very different than what they might experience in 100 years when they’re mature plants,” says Heyduk. This truth is a reminder of the precarious, uncertain state of Joshua trees’ future as climate change continues to transform their habitat and ranges northward.
Continuing their work, researchers have recently pointed out that there are important physiological differences between the two species of Joshua trees. It’s possible that these tiny variations help them get through the changing environment and on to the next generation. Nevertheless, as Heyduk notes, more research is required to better understand these disparities first.
“One of the mysteries has always been, why do these two species persist? There are differences in their pollinators and their flower structure in response to the pollinators, but there are also some hybrids. In future work we will explore whether or not the physiological differences are also part of why these species continue to exist as two separate entities,” – Karolina Heyduk.
This long-term project aims to address how these fascinating and beautiful species utilize their habitats. It further measures how smartly they are learning to translate those investments into concrete solutions that climate change is forcing us to answer.
Bridging Research Fields
The study on Joshua trees spans several biological disciplines, from ecology and population genetics to plant physiology. From these different physiological traits, gene expression level and accumulation of metabolites have been measured by researchers. This hands-on approach better equips them to know how these trees grow and flourish out in the wild.
This detailed scientific approach paints a rosy picture of how adaptable Joshua trees might be to a changing climate. Perhaps most importantly, it calls for more focused research to better understand the impact on desert ecosystems. Until now, these areas have come too far down the priority list compared with other ecosystems that are facing the wrath of climate change.
“We’re bridging a lot of fields in biology. We measured a lot of physiological traits, but we also looked at the gene expression of these plants in the gardens, and the accumulation of metabolites, which are compounds that plants make,” – Karolina Heyduk.
Scientists have expressed increasing concern about rising nighttime temperatures in addition to soaring daytime heat. This observation suggests we need to reconsider some long-held assumptions about how resilient desert plants are.
“We’re not focusing on desert species quite as much as other ecosystems. I think partially that’s because we think they’re already adapted to the super-hot environment and they’ll be fine,” – Karolina Heyduk.
However, as scientists observe rising nighttime temperatures alongside daytime heat increases, it becomes clear that assumptions about desert plant resilience may need reevaluation.